Discovered a little niggle with my JDM Blobeye STI when having a 'spirited' drive with a BMW M5 a week or so ago, private road of course.

When in 6th gear and under full throttle (was at around 80-90mph when this happened) the car suddenly stopped pulling, almost like someone has killed the throttle. You can keep your foot down and it will pull through, or back off then come back on the throttle and it sometimes doesn't happen again.

I did hear a clunk type noise from the gearbox area when this happened, but unsure if that's just down to the load being taken off the box in such a short space of time.

The gearxbox performs fine, no whines, knocks (other than the one I described) or crunches and has enough clean oil in (I checked a few weeks back).

Where should I start looking!?

 

what does it pull like in 5th

 

Fuel cut?.

 

Absolutely fine in every other gear.