Specialty File
SLP Engineering slid off our radar screen about four years ago when the General lowered the boom on the Camaro and Firebird. Now SLP is back with a pair of new performance packages for GM's 400-hp, 6.0-liter LS2 engine - a $4550 kit for a Pontiac GTO and the same deal for a Chevy Corvette at $5900.
And if that's too much, do the 12-to-18-hour installation yourself - the kits come in the mail for $3050 for the GTO and $4400 for the Vette.
SLP is no aftermarket tinkerer. From 1991 to 2002, the Toms River, New Jersey, firm turned out about 52,000 pumped-up muscle cars-including Camaro SSs, Trans Am WS6s, and Firebird Firehawks-that GM sold in its showrooms coast to coast.
The "Performance Pacs" add 65 horsepower to the Corvette and 55 to the GTO (the latter makes less power because of a more restrictive intake). The performance pieces include higher-ratio rocker arms, larger and better-flowing stainless-steel headers and exhaust, high-flow catalytic converters, and a high-flow air filter (on the GTO) or a redesigned air intake (on the Corvette, one reason its kit costs more). SLP retunes the engine controller to mesh with the new parts and provides a three-year/36,000-mile warranty.
Here's a look at our experience with the two breathed-on performers:
