Just wondered if anybody can shed any light on a problem im having. When i drive my car under load e.g 30mph in forth and let speed build up occasionally it sounds like the clutch is slipping. (revs sound like they go up then drop back down again) But the car still speeds up. If i let off and put my foot down again it wont do it.

When i eventually got it to do it again, I had a look at my boost gauge and it seems to drop boost. The car has recently been in for a new ported and polished had and has had a full setup. Has anybody had this before.

Any help would be much appricated.