i was running frpp whipple H.O. with 3.375 pulley making 11 lbs. of boost and dyno'd at 469 rwhp. i added 1 3/4" kooks LT and 3" catted h pipe and boost dropped to 9.5 lbs. and dyno'd at 455 rwhp. i would like to get some boost back to 11-12 lbs. what pulley should i change to? 3.125 or 3.25 or reichard racing 3.1 or 3.2

 

Was everything exactly the same on both dyno days?

Did you change gear ratios?

 

same dyno! mustang dyno! weather was same for both days! gear ratio was 3.73 for both. the 469 rwhp was using the tune that came with the voucher procal tuner with the kit. the 455 rwhp was the tune done by the tuner. the kooks headers are 1 3/4"

 

The drop in boost is common, with better scavenging from the long tubes the cylinders will evacuate the exhaust a lot easier but you have a crappy tune, the power levels should be exact being you're still getting the same volume of air.

 

that's what i thought too. i spend $2900 at this shop and lost horsepower. along with damaging one of my foose wheels. not giving me a lead wire for my wideband back or not drilling the hole for the sensor like i paid him to do!

 

i'm running the 3.125 pulley and saw 12 psi today during
a couple WOT runs, i have stock exhaust.

 

I dont think I have ever heard of anyone losing hp with long tubes. who did the tune?

 

Don Lasota!! have you ever heard of him? him and his son were doing the tuning. i dont want to say anything bad but i just want to know how safe my car is. did i get a bad tune that was suggested? i did run the car at the strip and it ran a 12.004 at 124 mph. with drag radials.