Actually, is the solenoid pressure activated? Why can't I release some pressure to trick it then?

The s5 also has higher compression to give it a little more power. $4000 is a reasonable price for an s5 in pretty good condition. I bought mine ('89) for $2500 with a blown motor. The best way to gain HP is with a down pipe and mid pipe b/c when you remove the cats the decrease in back pressure gives you more boost. If you're gonna get exhaust go all out and get the Racing Beat full exhaust. Looks nice, sounds even better, gives you nice power increase, and it is some high quality ****. I bought it and never regreted it. Possibly the best mod to my car so far.