Where's the boost? whipple problem
 

I have a whipple on my truck and have been running 11lbs of boost for months. I recently changed to a ported throttle body and right around that time, my boost started not going above 7ish. I don't get it. Can't figure it out. Steve at whipple claims I must have a clogged exhaust system. he says if i'm running that much boost on stock cats, i probably melted them and that sent debris into my muffler causing a backpressure problem. Any thoughts on this? I just ordered new dynatech cats and a flopro muffler. What else could be the cause? I have new plugs and wires and no misfires according to my hptuners. Also, not running the whipple computer. I have larger injectors, inline fuel pump and Nelson tune.

nobody?

My guess would be the cats. Although, every flow mod you do to the motor to allow it to move air more efficiently, the lower the boost will be. But i dont see a ported TB stacking 4 lbs of boost. In the mean time you COULD swap back to the origional TB and see what the boost does. If thats not it(which I dont think it is) it could be either a boost leak or cats. On the other hand, I thought clogged cats would stack the boost as well. Hmmm....

I know in my GTP, when I changed the DP to 3" from the stick 2.25 I.D, and removed the cats I dropped around 4psi of boost.

Although it could be the cats, seems weird since LPE uses stock cats on the TT cars they build.

I also have a whipple just so you know. I would definitely dump the cats for that much boost. Run some test pipes in their place until you need to do emissions. Sounds like you might have less boost because you have less restriction into the throttle/intake. Restriction will make your boost pressure go up, less restriction with the same pulley will show less boost but make more power. The same is true with your exhaust. It's also possible to have a vacuum leak so check for that with some carb cleaner around your new install.