1991 RS 305

Stock 85 TPI 305, 50,000 actual, with typical free--low buck mods. I'm installing a Dynomax Ultraflow Welded #17227, 3 in inlet with dual 21/2 in outlets. This car has the wide mouth , 4 bolt flange cat (gutted). It also has the stock TPI manifolds and Y-pipe. Its a 3 inch pipe coming out of the cat which funnels down to 2 3/4 into the stock muffler. Would a 3 inch pipe from the cat all the way to the muffler help the flow a noticeable amount? Or would I do just as well with an adapter on the muffler end of the stock pipe which would go from 2 3/4 inch up to 3 inch into the muffler? This Dynomax is a very free flowing muffler. This may sound wacked, but could the 3 inch pipe possibly cause a loss in bottom end torque with the Dynomax due to too much flow? Thanks in advance, guys.

LastViceRS

If you intend to install headers and a 3" Y-pipe at some time, I'd get the 3" intermediate pipe, but if not I'm not convinced you would see an improvement over the 2-3/4". Conventional wisdom has it that your most severe restriction is in the manifolds and Y-pipe(I agree). As far as loss of low end torque with the 3" pipe, I plan to eventually go with headers, 3" cat, and 3" catback on my LO3, I get mixed opinions when I ask the same question of others, but I'm going to roll the dice on this one...