93 5.2 runs bad when cold

[recian]

I've got a 93 B250 im helping a neighbor with. I know its not a ram but it's the same 5.2 magnum in gen1 Trucks. I'm no stranger to these. Haven't dealt with many with EGR tho. Haven't seen this issue before. It won't idle when cold. Have to hold throttle open a little. Same at all temps. At first i thought typical IAC valve. I threw one in and it kept idle. Worked for many days. Cool. On to problem 2. I took front of engine apart to change a ruptured heater hose. (Just the bracket and alternator) and replaced cracked coolant sensors. After reassembly i noted idle issue returned. Vacuum is very low around 10in or less when this happens and it'll bog down and stall. Holding throttle it stays around 15 in and after maybe a minute truck will hold idle, a bit rough around 15. Before this point if you push throttle, it bogs and vacuum goes to 0 and maybe a second or 2 itll rev up like its bogging bad. Randomly it'll idle up a bit, no tach so i cant confirm rpm, vacuum goes to 19 and it's smooth as silk. Like flipping a switch. Snap throttle and vacuum hits 0 for 0.2 seconds then responds instantly and it revs quickly and smoothly. Now it won't stay running when cold. I think that "flip" when it begins running good is open loop flip. It won't idle up when cold. It seems the IAC isnt opening as much now. RPMs stay low when cold but raise when vacuum increases and truck begins to run good. Confirmed ecm coolant temp resistance is around 5k ohms when cold and 1k ohms at operating temp. The old one read 17k ohms when cold. According to chart, 5k is around 90-100F which is slightly high. Voltage goes from ~3.8v cold to around 2.7v warm. Im curious if this sensor isnt going cold enough. I know the converter is bad, it rattles and he has a new one in the back but I'm not welding it in. I'm thinking he should get that converter replaced first. I'm just not confident that's his only issue.