if you have it stuck on open it's going to run stupidly rich at all revs up to about 6000 and do some serious carbon fouling, as well as give you very poor MPG.
But the worst part is, you'll also get poor performance..
The only way to run (a little) faster without the boost is to have more open exhausts (Kerker for example) including the headers as slip-ons won't make a change, and install a stage 7 kit (or better Morley's Muscle kit) in the carbs.