Well I was rolling with my cousin on the 15 freeway. She was racing this benz and around 3rd switching to 4th maybe around 100 dont remember exactly, well anyway right after that her car just jerked and seemed liked it hit fuel cut.

So right after that she let off the gas and was pacing with the others, then we noticed that the speedometer was flying off the roof like it would jump between 60 to 100mph then drop to 80 and stayed their for about a second and then it would go again.

Also she can't hit full throttle on any gear because it would just jerk.

I'm thinking she's misfiring or fuel related, but I cant really check the car because Im really busy tomorrow, on top of that one of the bolts of her apex exhaust fell off and her car was so loud and annoying. Man we thought she blew her motor haha.

Mods
Big 16
FMIC
CAMS
usual upgrade...

The only thing I could think of is when the car hit fuel cut, the engine moved so violently that it kinked or broke the speed sensor in the tranny. Other than that, the two should not be at all related. (fuel cut and speedometer)