Only thing I know that could cause this is intake pressure blah blah blah, bad pcv valve and so on and so on... but my 5.4 has BAD build up in the intake, 1/16 inch this everywhere from the butterfly down.. found this because it started smoking.. tell me how to fix it properly. I have my ideas but at the same time I want advice, keep in mind I may pull it in the next week to put some hotter cams in.... thanks
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*crankcase pressure