Did a search on car-parts.com and I need some help.
For the 99 Max, there are two different production dates on that site. Thru 9/98 and the other one is From 10/98.

My car's production date is 12/98 so I'm assuming I should get the 10/98 one, but I want to be 100% certain that I get the correct ECM. Also what's the difference between the two different production dates if they're both '99s.

 

From 10/98 might be Cali Spec emissions.
Might also have something to do with the immobilizer system, but I think that was in all 99 models so...IDK.

 

NATS system was all '99s. There are also 10/98+ ECUs with Fed spec emissions.

You're correct, just get the 10/98+ ECU. Was there a reason you thought you'd need the other one?

Pre 06/98 is MY1998. 10/98+ is MY1999. That's the difference.

 

Thanks for the confirmation. I'm having some issues with my car and seeing as how I've tried everything else, I'm leaning towards a bad ECM. Damn timing keeps retarding severely every now and then, sometimes by as much as 20*. I have no idea what's causing this. Tested coils, injectors, both CKPS and CMPS, played around with 2 different TPS, will swap another MAF this weekend.
The one thing that caught my attention is that the Suprastick is messing with the TPS voltage resolution. When I disconnect the throttle position wire from the suprastick, voltage range is 0.4-4.30 but when its connected, it's 0.4-4.00. I wonder if this could be the problem.

FWIW, right now I'm running off a cali spec ECU and my car is Fed...I dont think that would be the issue.