[radz28]

Replacing the lids and baffles on 4th Gens was usually good for around 10 RWHP according to tests I've read by different sources. LT1 intakes were sometimes good for more! I think that the GMPP system will add between 5 and 10 RWHP mostly due to replacing the tubes/baffles with nice round tubes. It'll probably give a little more intake roar but I wouldn't expect too much. The computer will likely be able to compansate for a little extra flow, but tuning will make the most of the mod'. The factory usually tunes the car pretty conservative and rich, to protect the engine, and tuners, by and large, seem to lean them out most of the time and get that AFR around the mid 12s. Each combination is different and FI tunes are usually, from what I've read, in the mid-to-upper 11s.

Back to the GMPP intake, I think about 10 RWHP will be about the most one can reasonably expect from the mod'. It looks better and should flow better, at no cost to water getting into it, so it looks good in my eyes.

JMHO.