I'm in the same boat as some of you, no factory oil cooler with step AT. I was at the track for my second time last month and the only session I didn't hit limp in was the very first. Mind you, temps were in the 30s during that session! I had to cut my day short because I was becoming a rolling roadblock for the other drivers.
I'm adding a Stett Stage 2 oil cooler this Friday, so I'll post up the results of my next track outing. By the way, I participated in numerous AX events last year and never hit limp despite blazing summer temps here in TX.
This year I plan to do a few less AX events and a few more track days, so the cooler is an absolute requirement.
'07 E92 BMW 335i