Tony, you're welcome. I still don't think the PROM is a good bet because the TSB was not a recall. It was a remedy to customer complaints about hot idle surging & fluctuation. If the ECM was replaced by a dealer they proly talked the customer into an updated PROM if they were looking to pad the job/bill at a low cost-hi profit margin....I bought the updated one for my 90 and it only cost like $35 from GM. The ECM's don't come with PROM's, so you have to do the transplant if you swap ECM's, but you proly know that, I'm just covering all the bases. I didn't know beans about EEC systems when I bought my Z, boy o boy am I getting edjamacated...
I come from the holley carb generation!
When your state does the idle test did they give you the print out of the results? If so then tell us what they were & it would help the guys analyze the issue.
Does she smell rich or lean? What was beyond the limits?
If I can do this correctly, someone posted this awhile back vis a vie smog testing so I put it in my favs because I'm so behing the curve with this stuff.
http://www.aircare.ca/index.php?repi...-causes-hc.php
I'm just not good with this stuff yet!
Tom