'89 F150 5.0 XLT Lariat / Manual 5 spd (OD)

ECM is cleared of codes and no codes have been reloaded .
Still on first start up motor will idle up to 1500 rpm then fall , maybe a little stumbling before cutting off , I can then turn the key again and it will idle up to 1500 rpm and then slowly fall to a smooth idle about 700 rpm just fine ..............the second time.
Also new issue today where motor will not start when hot or run for a bit , can turn off key and re-try and sometimes will fire , most times just have to crank for long periods to get started .
Fuel pumps have been replaced (all of them) , relays are good , they look new as well , tank switch working , tank switchover control was recently replaced as well , also ign coil , cap , rotor , wires and plugs are new.
Before I purchased truck the previous owner had all previous items replaced ( over $1000 ) , have a receipt and confirmed myself .
Have bled fuel rail today , added seafoam for GP , verified fuel filter is new and clean , problem is present regardless of tank selected.
Will chjeck fuel pressure on rail tomorrow to see if possibly FPR , also will try to re-produce issue with not starting and verify I am not loosing spark , the truck only has 60K on it original , the only thing regarding ignition that I know has not been replaced is ignition pick up.
I have personally replaced TPS and cleaned IAC , IAC was not very dirty and from what I understand may be cold start issue but not sure now with this new development which may be the same issue just getting worse.
Outside of taking FPR pressure readings and verifying not losing spark , any other ideas , could it be the IAC and if so is there a way to reliably test IAC , I have priced it and it is $70 , pretty pricey .