Help with fuel cutoff (?)

[bigchallah]

Had a weird problem at the track yesterday. Car was running a bit hot, but nothing crazy. Once I got about halfway into each session it started severely cutting down/off the power at EXACTLY 5000 rpm's in 5th gear. Once I climbed to 5100 power returned. This happened over and over all day, eventually I started noticing the same in 4th gear but at 6000 rpm's. I'm assuming this is some kind of fuel cutoff.

I am far from a mechanic, so please feel free to tell me the most obvious of things I should be checking. Any help is appreciated, everything I know about the build is below from a previous for sale listing:
https://www.bimmerforums.com/forum/s...e-Car-For-Sale

[ScotcH]

fuel filter, failing pump, ignition coils. Did your speedo act up at all? Could also be speed sensor …

[bigchallah]

fuel filter, failing pump, ignition coils. Did your speedo act up at all? Could also be speed sensor …

Thanks for the response, that makes you the second person to bring up the fuel pump. I just don't get how that would lead to this much consistency in the behavior (5k rpm in 5th every dam time). Speedo did not act up that I noticed, of course I was on track so not watching it heavily.

I called active who makes the chip and the lead engineer "guessed" at a crankshaft sensor. I know the common issues with that would cause it to have starting issues, I didn't experience that at all.