Bill has posted some nice threads.....But if for any reason you feel that the upper/lower intake manifold gasket is to much to do at the momment, just try cleaning the entire throttle body, make sure the EGR pintle valve isnt sticking(clean EGR passages while your at it), clean IAC valve, chech IAT sensor, check/ clean MAF(Im not a big fan of cleaning MAFs but sometimes it does work), make sure air filter isnt clogged/dirty. Those are the really easy simple things to check....fuel filter is deffinately a possibility. And also, your sensors may be intermittent(voltage dropping on loads)
Again, this is easy stuff to start off with, but with 177k it may very well be the UIM/LIM gaskets but if you've been maintaining ya motor it may not be. 177k is plenty though, but just inspect all around ya plenum or s/c for signs of wear and tear and check ya oil(make sure its no other color than it should be)
