its an original ford intake manifold from 69, it was hot tanked and blasted about a year ago, and ran fine for 4000 miles, whole engine has about 4000 miles on it... i hardly doubt any critters crawled in though, i live in san diego... this problem just started happening after i pulled the engine out of my 69 galaxie and stuck it in my 66 mustang.... i'm starting to believe something went wrong in my heads, because the machine shop that did my heads was a wee bit shady, but only charged $70 to do both of them seeing that i supplied all the hardware...so i think I'm going to take them in to a much more reputable machine shop and have them take a look at my heads.... i'm just very unhappy about having to pull the intake manifold and heads.... i never like doing it...