I would imagine you have a vac leak somewhere, maybe you can find it with a can of ether... might be hard if the leak only occurs during higher boost...
There was a thread some time ago about going through and using clams on all of the vac lines being good for squeezing the max amount of boost. Seems like the author of the thread posted an acutal gain in boost after doing this...
Not to get off topic too much, but how is that 15% working for you, other than the current boost problem? Do you think it is working OK?
I have a 5% jackshaft on the way, and already have a 10% blower pulley, I also have a double IC being made (aready have a IC fan). I am toying with the notion of using them both... Do you have any problems with pinging? Have you tuned the car since the 15% OD?
After secod though, I bet you will be smokig after that snow kit
I'm still hoping to fit one in my buld somehow...
One more thing, that 14.7 was before these mods, correct?
Thanks!