ICS Performance. You've heard the name. And no, it doesn't stand for Incredible Chonis-Staining Performance, but you'd think so after a ride in one of these cars.

The name should be familiar, since these pages recently featured its ridiculously powerful E36 BMW M3 with a four-digit dyno readout that breaks tires loose at speeds over 120 mph ("World Eater," July '06). The madness continues-this time with totally streetable convertibles that'll embarrass 95 percent of the exotic and musclecar world in straight-line performance. Imported Cars of Stamford's shop has taken what once were justifiably wolves in sheep's clothing and basically scared the wolves out of them. They stuffed a tiger in one and a lion in the other.

Nothing on the outside of the yellow car is telling you this Z3, which was a 2.8L, is actually sporting a 240-bhp engine from an E36 M3. The air-to-air intercooler behind the bumper is the only thing giving off any hint that this car may shock unsuspecting motorists.

It was initially powered by an M50 2.8-liter six-cylinder, but the owner wanted more power. He had an RMS supercharger system installed and the car put down a healthy 335 hp at the wheels. He felt that still wasn't enough and brought the car to George Kakaletris of ICS Performance, who fitted an S52 3.2-liter engine from an OBD-I M3, but with the freer-flowing OBD-II intake manifold from a 325. Kakaletris then ditched the supercharger system altogether and replaced it with an Active Autowerke turbo kit, which uses a Mitsubishi TD06 20G turbo.

ICS added 440cc injectors, a BMW 540 3.5-inch air mass sensor, Plasma ignition coils, and lowered the compression from its stock 10.5:1 to a lower 8.5:1 using a 0.140-inch-thick VAC Motorsports head gasket, clamping the head back down with 10mm ARP studs. ICS also fabricated the three-inch full turbo-back exhaust to let the system breathe. When the engine was finished, ICS turned it over to Technique Tuning, where Nick Glantzis and his tuning expertise whipped out an impressive 411 wheel-hp at 5200 rpm, with a tarmac-thrashing 440 lb-ft of twist at 4500 rpm.

If there was ever a car that felt like a sledgehammer when hitting its powerband, it's this. I don't know and I can't entirely explain it. I've had this same turbo kit on my M3 before, but this felt way different. Maybe it's the reduced weight. Maybe it's in the tuning. Whatever the case, come 3500 rpm, your internal organs are wrapped around your spine. With more than 400 lb-ft available from 3700 to 5000 rpm, this car is a definite torque monster. And putting that power to the wheels is a UUC Motorwerks clutch and flywheel.

Keeping the car firmly planted (but also helping to reduce the potentially tremendous rear squat) is a Dinan stage-two suspension system comprised of shocks, springs and anti-roll bars. This setup maintains a completely streetworthy feel.

Following the car on public roads is hilarious. You're cruising at about 40 mph, when suddenly the car's rear end hunkers down and shoots itself into a tirespinning fishtail with a quick, noisy blast of either black smoke or a burst of blue flame from the tailpipe on the upshift. If you haven't heard the sound of 400-plus-whp blasting out of an an S52's tailpipes, you don't know what you're missing.

The silver M Roadster is a completely different animal. Having been supplied from the factory with the 333-bhp S54 motor that went into the E46 M3, this car already had a great start in the power department and was definitely a sleeper. But its owner's quest for more muscle resulted in a Vortech supercharger system finding its way in the engine bay.

Not surprisingly, ICS got its hands on this car as well, but this time the supercharger stayed. However, the engine was fully redone for added reliability and flow. At the bottom end, a set of CP Pistons lowers its stock 11.5:1 compression to a safer 9.5:1, and Pauter forged connecting rods are attached to them. They spin around a stock crankshaft secured with ARP main studs. A modified oil pump was installed for more pressure.

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