In my opinion this is one or a couple things going on.
If you follow the IAC and TPS trace across RPM, you see that RPM refuses to fall against a completely closed TPS and IAC. That means air is getting into the engine somehow. That could be:
1. Out of adjustment butterflies
2. Vacuum leak
3. Leak in the IAC valve
You should almost never see a completely closed IAC, 100% closure would mean the system is trying to kill RPM. At idle you'll have it open slightly. You see this accurately on your log between 35 and 55 seconds.
If this was an issue I was facing, the first thing I'd do is get some carb and choke cleaner and clean the throttle bores, IAC port, basically everything on the unit really well. I would do an extremely thorough check at this point for vacuum leaks at the carb flange and the intake manifold/head ports. If that does not cure the issue, I'd then go about resetting the butterflies by going through the IAC adjustment process outlined in the Sniper manual. Finally, I'd look at replacing the IAC valve/motor as it's likely not acting in accordance with what is being commanded.
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-Jason
1969 Pontiac Firebird
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