Are you driving a slushbox?
I haven't noticed any significant throttle lag on my 128i, but I hear the auto trannys are worse about that, which is why I ask. Also, I'm thinking an auto tranny might overheat or something on the track, which could be a source of your issues. I've heard of auto-box 135i's/335i's having a harder time with going into limp mode at the track, so could be a similar issue.
But if you're driving a 6MT, I don't know. My 128i hasn't had that problem. Did four 20-30 minute runs a couple of weeks ago, and am on PSS's, so I was pushing as hard as I dared. Any chance the hesitation was the DTC cutting power due to loss of traction from the all-seasons? Just kind of brainstorming here...
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