should be remarkable changes when it goes into closed loop.. what MV is your 02 sensor reading cold, then warm? does the idle go down when it goes into closed loop? EGR is a likely spot for a vacuum leak, you can take it off and test it.,. if its letting exhaust gas go into the intake at idle theres a problem. check your brake booster too make sure the hose or the booster itself isnt leaking. make sure the round gasket on your IAC isnt leaking. if u have to, u can make a little homemade smoke tester with a coffee can and air pump and smoke it. these iron intakes and heads dont walk much, its usually not a vac leak from the intake to heads on these, its likely the TBI gasket, EGR, VAC HOSE, ect.. if your going to keep the truck, I would highly recommend getting some type of scanner that can see whats happening.. I got a actron CP 9690 for abt 180.00 and it is great for these old trucks. it has adapters for obd1 and 2 systems. when u can see all the data , what the 02 sensor voltage is, battery volts, fuel trims , IAC position, map votage, ect, it really makes it ALOT easier than guessing. Once u get the truck running good, you can record and print all of the PID data, for reference , so if it starts acting up again, u will have a baseline to look at, when it was running good, then pick out the stuff that is different.
