Hesitation in 3rd gear ... feels like 5th ???

[rene525d]

Guys,

recently my 2004 Boxster S has been showing a hesitation in 3rd gear, to the extent that sometimes I wonder if I have in fact engaged 3rd and not 5th gear. It happens only when I max out 2nd gear - 6800-7000 rpm at 103-108 km/h and change into 3rd gear. Until it reaches 135 km/hr, which is about 4500rpm acceleration is very very week. Feels like it is running lean. After that it seems to pick up as normal. Off to forth gear and everything is fine. Had codes read, nothing significant.

The only change I recently did was install a BMC, but I replaced it temporarily with my old OEM one and the same happened. Last week at the track when I was in Sicily there was this stock Toyota Celica (190bhp) and in 3rd gear on the straights he was catching up with me. My mate driving an S same year as mine managed to increase the advantage ..... any ideas??