I have a 2017 M140i manual with a stage 2 map created by a reputable local company, a mst intake, and a decat downpipe. I had no trouble at all keeping the vehicle stuck in any gear before I got the map.
At approximately 140–150 mph (on private ground), I have a big backfire and plume of carbon dioxide out the rear, although this only happens when I hit about 5,000 RPM in fifth gear, according to the map, at which point it somewhat reduces in power before kicking in again.
The coil pack is good, and the NGK iridium plugs I placed have reduced the issue to a negligible degree, so I went ahead and installed them.
Has anybody ever seen this, or do you have any suggestions, or am I simply the victim of a **** map, or is it time to whack the head off?