With the cobalts, you can throw ridiculous amounts of boost at the engines as long as you have a H20/meth injections. There are 9 second balts running around with 600+ whp on stock blocks. They need some Carillo rodsd though as the stock rods will start bending at like 550-ish whp. The most I have seen on a stock turbo is like 425wtrq and about 380whp. That was on 26psi with straight E85 on an LNF. And that was a car I was helping tune. Its a Saturn Sky Redline (watch out for the black one with white strips, tis a beast.
Guy, just FYI there are a few 800-900whp cobalts running around the streets lol. Look up ZZP. They build literally some of the fastest FWD cars ever. on cobalt started life as a 06 SS supercharged balt. It then got a MASSIVE turbo, runs like 50psi on a stock-ish (girdled) block with a new lower end and some head work with cams. they were trying to break the block and just kept turning the boost up, but they ended up popping the head gasket instead. I love how strong this little motor is.
http://shop.zzperformance.com/store/default.aspx
Granted these full setups cost like 10k but for less than $30000 you can have a car that is about as fast as anything out there. And you can get it in a RWD platform as long as you don't mind running around in a Saturn sky or a pontiac solstice. haha ew