The difference in the pulley is only 1 psi boost, from 75mm stock to a 72mm. That is about 10-15 HP, not much in the big picture. We recommend that with the upgrades he is doing already there will be plenty enough power increase to warrant not using the pulley. If he feels like he needs a little pick me up in the future it is an easy swap. I told jlatigo that the smaller pulley would require an idler and still retains the factory length belt since the Roush is an odd ball length. A 90mm idler will take up the slack, that is what most guys do using the 72mm pulley.
The Roush is a different animal than the Whipple blower, it uses smaller diameter blower pulleys which is going to put less belt wrap around the pulley. Your more likely to see belt slip or the belt jump off unlike the Whipple. Hence the fead belt guard. There are issues tuning related with shift points that will create the belt to jump as well. We have our tuning dialed in, that won't be an issue. However since jlatigo said he likes to do offroad and aggressive style of driving I took a careful approach into his upgrades and gave him room to improve down the road if he chooses to do so.
Parts should be on they're way to you ASAP!
JimIII
The Roush tuning leaves a lot to be desired, but because i didn't know any better i was perfectly happy with it. Unfortunately i got the opportunity to drive the Shelby Raptor at TRR and that opened my eyes. My suspension is somewhat like theirs but with more capability but my motor was severely lacking in power and throttle response for my new wants and needs. Based on what i have read about this and, testimonials from others using your products i am confident that these upgrades will get me where i want to be. If not i guess there is always the pulley change? lol
Thanks Jim, i'm like a kid waiting on Christmass to arrive!