My car is an MY00 with Prodrive pack + high flow downpipe and 65000 miles dispatched. In the last three months it has had new plugs, ignition leads, mass air-flow sensor and a boost solenoid (used). There are two problems which may be linked. When driving gently (changing gear at 4000r.p.m. or lower) all is fine. But if driven harder then when changing from fourth to fifth gear the change is always crunchy. This seems to be because the revs do not drop off quick enough when the throttle is released. In addition to this there is some hesitation in top gear when driven hard. This is most noticeable if I sit in top at 100m.p.h. and then floor the throttle (this just happens to be the speed at which max turbo boost is there immediately) and can be felt as a slight 'holding back'. It can be felt most between 100 and 120m.p.h. and then as the acceleration drops off it is not so obvious. If I sit at 80m.p.h. and floor the throttle then if the car is holding back then it is not noticeable.
Any ideas?
Kevin

 

Kevin, The first issue, (gear crunch) sounds very much like the synchro on fifth, either that or the retaining nut on fifth is slightly loose, could be either, best get the box sorted, as if it's the nut loose, then more damage can be done by leaving it, the good news..if you call it that.. is that this can be fixed with the gearbox still in the car.....

Second issue sadly i cannot comment on......

 

second issue could be slight overboost caused by the cold weather atm. other suspects would be the plugs but you have changed those.

clean the boost solenoid (located by alarm siren on drivers side), do a search for this there are a few guides.