E39 M5 track car build throttle cut issue retest

More testing. The full throttle cut has disappeared and now just breaking up. Theorizing water and varnish still in the fuel from the tank before I bought it. I siphoned out the pump side before installing the new pump, but the tank is a "saddle" design with a siphon pump between sides. I didn't clear that side. ISO HEET fuel additive has been put in the tank in hopes of continuing to clear the tank if that's the issue. At the end of this one I finally got an SES and misfires enough to shut down cylinders. I had to restart the engine to clear it and have all cylinders back.