Hi, I have a WK Caprice daily that I am trying to maximise low down torque and fuel economy. At the moment I have a 3.5 inch cat-back Sureflo system in "quiet" that I am very happy with. I have a Maf-less tune and a Duspeed OTR which I am also extremely happy with. The car get really good economy and my next mods are going to be an eaton trutrac with 3.73's and extractors and cats. My question is this: 1. Should I get Pacemaker tri-y's in 1/5/8 and a 2.5 inch collector and get 2.5 inch 100 cell cats or 2. Pacemaker tuned in 1/3/4 and the 3 inch collector and 3 inch cats. The reason I ask is that if I am going to all this expense I would rather get option 2 for the best flow but the reality is that I never reve the car out and mainly use low revs from 1000 - 4000. Would there really be a torque difference between the 2 especially with the diff gears and touch up tune?? Thank you. Some original photos have not been recovered yet.