Replaced stock with a 3" inch MAG Comp. CB. Retained Stock-Hipe and all cats. The butt dyno is registering a reduction in HP and Tourque. Is that possible? Does larger diameter piping recduce the backpressure and result in the sensation of lost power? Are there any dyno charts out there to speak against this?

 

It changes the rpm where the power peaks, moves it up to a higher rpm so you may lose some down low but gain it back higher up.

Get a tune that is adjusted for it and may gain some of the low end back.

 

its still breathing thru the stock cats so the exhaust will do nothing.. Remember.. And exhaust system only flows as well as the most restrictive part. No tune is needed..