90 5.0L LO3 rado EXTCAB idle and high rev
 

well so far this truck is truning out to be a BOAT(break out another thousand ;p) and I really dont want to end up replacing everything so here we go with a list of symptoms

when first started engine idles fine, but i have found that if I do any hard driving, ie; full throttle through a couple gears, it will no longer idle properly, infact will idle to almost 2000RPM some times, but if I turn it off, then back on, it will idle just fine again(im thinking possibly dirty TPS, faulty IAC or something along those lines but not sure which.

Something I have noticed that seems to be every so slightly getting worse or I am just becomming more aware as I keep my ears open for any sounds my vehicles make(years of runing heavy equipment have tought me this) at highway speeds when the motor under full load and at fairly high RPM i would say 3/4 to REV shift limits i can feel and sometimes hear the engine missfire consistantly untill I let off the gas or it shifts depending on speeds.

I am about to change the fuel filter and take off the throttle body and clean it after i buy a gasket for it. but i dont want to start buying sensors all over the place as our 89 2500 4x4 has just gone through the same problems of replace everything to find out our good ole ac delco plug wires got fried after maybe 10k.

any help suggestions and wild guesses are more then gladly appreciated, as well one more thing, I would like to find a locking diff to fit my silverado, any specs would be helpful to look for, and as well what tranny's could I swap or do I have old faithfull in mine?

project in hand is to make a 327 that lays 100 feet of rubber instead of my 305 and 50 feet :). As well have plans for a 90-95 4x4 project soon to start this winter, looking for a donor as we speak :)

fixed the issue with up and down idle, throttle body gasket was horribly bad split broken disfigured LOL, now i have to figure out where the hell the wire is so I can properly time this thing, some on has it set @ 33deg, and I cant time it right until I disconnect the wire to the ECM still looking to see where it ends up, let you know more as I go :)

it is either under the dash or under the plastic cover on the passenger side firewall