You have to wonder why Chevrolet developed one of the fastest production sports car in the world and then camouflaged it to keep it a secret.

Except for a slightly different rear end configuration, the high performance ZR-1 offers little visible evidence that it differs from the regular Chevrolet Corvette coupe for 1990.

If you look closely, the ZR-1`s body is flared from the door rearward to provide the room needed for the car`s massive 17-inch Goodyear unidirectional tires. The ZR-1 is an inch longer and 3 inches wider than the normal coupe as a result.

Rectangular taillights are the only other clue this isn`t the regular coupe.

Other than the styling, the ZR-1 is as difficult to get into or out of as the regular `Vette. The driver`s seat has that same feel of a corset strapped on. Tight quarters and little room to maneuver. These are `Vette trademarks.

Turn the ignition key and the 32-valve V-8 awakens. But it`s not until you turn a second key that activates the power switch on the dash that the 5.7-liter, 32-valve, 375 horsepower `Vette really springs to life and the ZR-1 earns its moniker as King of the Hill.

To ensure son, daughter or the parking lot attendant doesn`t get carried away with the engine`s massive power, the ZR-1 requires two keys. With the regular ignition key, the secondary port throttle valves won`t open; that way, the big V-8 develops only 200 h.p.

Turn the key in the power switch from normal to full and a light glows in the instrument panel to serve notice the secondary valves have gone to work and375 horses have been let loose.

Fasten the belts and hold on: You`ve discovered the reason some dealers are asking and some customers are willing to pay $75,000 for a limited edition car that carries a $58,995 manufacturers suggested list price.

`Vette engineers said they wanted to come up with a car that would strike a little fear into any driver about to punch the pedal. They succeeded.

To best appreciate the 375 h.p., we put the `Vette through some paces in the normal 200 h.p. mode. There were no complaints about the power or with the six-speed manual transmission, which was only a bit notchy going through the gears.

A console switch allows you to choose three suspension settings-touring, sport and performance. We tried each.

In touring you get a rather soft suspension setting, much like the Nissan 300ZX before it returned to being a sports car in 1990 and the luxury sedan suspension was scrapped.

In the performance mode, those 17-inch tires noticeably grabbed the pavement more firmly for tighter, quicker response, almost swivel-like turns. We had difficulty noticing any difference between the performance or sport mode.

Then it was time to turn the key to full power. Two of us left the light slowly together.

The driver in the Accord looked over and sneered at the `Vette alo ngside as if to say, ``Trying to keep up with an Accord?``

Discretion be damned. We hit the pedal and the sensation was as if we were propelled forward while the Accord was jettisoned rearward. The little compact became an instant dot in the rear-view mirror.

That power key activates a rocket. Fun, to be sure, but you need space to play with the `Vette.

When you move from zero to 30 miles an hour in 2 seconds and zero to 60 in 4 seconds, those widely spaced stop lights come up faster than the old Burma Shave roadway signs.

We found it odd that the faster the King performed, the less notchy the 6-speed manual transmission seemed to become.

The 17-inch tires did an admirable job of holding the car down and in line, though on a couple of occasions we wondered whether the 18- to 20-inch tires Goodyear has under development might not find themselves on this car.

To complement the power and bring the King back to reality, the car come s with antilock brakes as standard. As a safety measure a driver`s side air bag is standard.

We had but two complaints, other than the cramped quarters, which for some reason became more bearable the longer we played with the machine.

With the attention to performance and the absolute need for that second key to activate the `Vette`s optimum power, we found it out of character that you can leave the car with that second key in the powerswitch, without the chimes warning you that you left your lights on or regular key in the ignition.

The other problem we had difficulty with was the ZR-1 styling-the fact it differs so little from the regular coupe. Chevy officials said they felt that if the King design differed dramatically from the regular coupe, resale values of the regular coupe would suffer.

But when you have a $30,000 spread in price between the regular and the King, you sure feel as if the higher priced model deserves more styling recognition to set it off.

Reportedly a change is in the works for the `91 model year, when the King may get a power boost to 400 horses, which is what designers had in mind.

To aid in breathing and to cut down on underhood heat buildup, the 1991 ZR-1 would sport a pair of air intake scoops in the hood. Those air intakes, along with the flared sides and different rear end treatment of the current model, would help set the car off from the regular coupe.

There are two other features of note. The Corvette sports a new instrument panel for 1990. An electronic tachometer takes up half the space, a series of gauges the rest.

Dead center in the panel is the digital fuel gauge and digital speedometer. To ensure the proper care of your investment, keep in mind the 32-valve engine requires 12, count `em, 12 quarts of oil. Just in case you forget, there are low oil and change oil sensor light on the dash.

For $58,995 just about everything is standard, including power operated retractable headlamps, dual electric and heated mirrors, one piece fiber glass removable roof panel, electronic cruise control, air conditioning, rear window defroster, leather wrapped steering wheel, AM/FM stereo with cassette and power antenna, power door locks/windows/seats, power steering and brakes, and heavy duty Bilstein gas-charged shocks.

>> 1990 Corvette ZR-1
Wheelbase: 96.2 inches Length: 177.4 inches Engine: 5.7 liter, 375h.p.V-8 Transmission: 6-speed manual, Fuel economy: 16/25 m.p.g. Base price: $58,995 Strong point: Rocket Power Weak point: Styling of its own, bidding war >>