It's been a while since my last post but I finally broke down and got a replacement ECU for my S4 after hitting too many dead ends. The good news is, the new ECU has solved two problems; it now starts on it's own without starting fluid and the trailing coils now fire. That's a big improvement from the old ECU.

With that being said, two new issues have popped up. First, the cat is getting hot, especially in fast idle start up. It'll have a mild glow to it but improves a little after warm up. On the old ECU, this would only happen when I forced it to run rich by holding the AFM open. Otherwise this was not an issue so I doubt it's clogged. Timing was reset after installing new ECU. I think I'm running rich but it's hard to tell. Research suggests this is usually a rich fuel mixture problem or retarded timing

Second issue (and maybe related to the above) is once warm, the motor doesn't like the throttle punched. It will rev up if I go slow but falls flat if I go too fast. This wasn't a problem on the old ECU.

 

Your second issue could be a bad fuel filter or maybe you tps isn't working. Do a test of your tps to make sure it soomthly sweeps with a muiltmeter. Also reset your tps