When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
IMHO you will not get a power gain on a factory-stock engine.
But if I'm mistaken, and there are minimal gains to be made, then they would only be at the top of the RPM scale at WOT.
Even guys with blowers tend to keep the stock t-body, if that means anything.
Your mpg will be the same until you start flowing more air, wich will again be at the top of the RPM range. At anything other than WOT, there will be no effect to either MPG or power...because the throttle will be limiting airflow, so you won't be taking advantage of the larger t-body's greater flow. Assuming your engine can ingest the extra flow, which I don't think it can.
You won't see a big hp increase as such, you will notice a crisper throttle response, and easier reving motor in most cases. Your mpg shouldn't be effected, unless you hammer it alot.