Before installing the IAC - try soaking it in your favorite synthetic gun oil (NO SILICONES!!!) for a day or so first (point the pintle up and fill around it's base - I even bake mine in the oven to encourage oil-creeping!) -- not only with that loosen things up (be sure to drain-off the excess before installation) but it'll make it far easier to clean in the future...
A little flare is not uncommon; especially when the engine was shut off under load (a/c, fans, lights, auto-in-gear, etc) or not fully warmed, and subsequently restarted in better conditions (warmer or no lights or ...?)...
... The RenixII uses a b+ latch relay to hold power to the ECU after shut-down so that the ECU can open the IAC for the next restart (you gotta get SOME air in the intake so the fuel will get into the cylinders with something to burn). The ECU has no feed back on the IAC's position (in the "run mode" it's all about "more" or "less" - and there's no feedback without the engine running)... On top of that, the ECU also "opens" the IAC while the engine is cranking - so the longer you have to crank, the more the IAC will open when the engine finally fires-up (remember here that the ECU won't fire the injectors or ignition until it receives qty=2 CPS pulses after a valid transitions from the distributor's sync generator, or until the engine tries to fire in a limp-home mode in the absence of that sync signal - may take more than 2 full revolution of the engine, allows a lot of time for that stepper to open!)-- Of course, then, with a good TPS value (less than 0.8v) and solid data-clocking from the CPS the ECU will begin to control the idle by closing the IAC.
There are a few tricks to minimize the flair, but many will impact ultra-cold or low-density-air starting (up there in WI, you know all about them artic Lows that sneak outta Canada, eh??). We could banter those around here, or work em PM if y'wanna play around with a few of em!