Other than a vacuum leak why would IAC drift down to 0

[beasleyrb]

94 LT1 on run stand with Long Tube Open Headers. No emissions are on the engine and have been tuned out. Basically a naked engine with an alternator. The engine idles and revs up well but I noticed the IAC counts drift to 0 after a few minutes of running in closed loop. I checked somethings that I thought might be leaking and sealed a grommet where the air intake temp sensor goes in. I thought that might affect the MAF reading which also blink red (low). I did not find any vacuum leaks visually or with a tank of propane moved all over the intake.

I was wondering what other than a leak will cause IAC counts to go to 0? And, does it matter?