any pipe restriction (less than 3") with your 3" collectors from the collector flange rearward hurts you and not sure how much I go with this but many have said that reducing to 2&1/2 for tailpipes is acceptable cuz of the gasses cooling & shrinking & looseing velocity. #1 is noise management (how much are you willing to tolerate) VS max output. I think the best system is 3" cutouts right at the collectors either vacuum or electrical then T'd from there with 2&1/2" rearward with restrictive (quiet) muffs. this way the power and the noise is under your control & only there when you want (need) it. We ain't teenagers anymore. with the money in the hands of a (neutral) third party you open it up & ten seconds later it is all over ex the crying (collect your money/shake their hands/call it good!). they will never know what hit em