"There are plenty of S4's with S5 AFM's. It's just an electrical nightmare I don't want to undertake until I feel I need that 1-2 more HP."

But are those S4 cars running the S4 ECU or, as Chris suggested, have they been completely converted to S5? It would not be a big deal to splice an S5 AFM plug onto the S4 wiring harness as long as it will work w/ the S4 ECU. I hope it is illegal because I'd just as soon not do it as long as no one else does either .

BTW I got out about the time mods were allowed to ECU's - did anyone find any real gains from it other than adjusting or removing the rev limiter?

Bill