Vacuum Leak - Who Knows About This?

[CK34GT]

Hi All

I have been driving my 98 R34 GTT for about 3 months. I bought it stock standard and since fitted a 3 inch exhaust from the turbo back. The car was running fine when I bought it in Summer, but recently (over the past month or two) now that the weather is getting colder, I am having a very annoying problem when I put my foot down hard. The car seems to stutter (makes a bad stuttering noise) and lose power, only seems to happen in the cold weather conditions. The car seems to spool fine but when it reaches the maximum boost (running stock boost at the moment) it seems to just die in the arse and not gain any more power, this morning it was really bad as it is pretty chilly out there.

Has any one out there experienced any similar problems on their R34's? I do want to add that the car was having the same problem before fitting the exhaust.

I think it may be a vacuum leak or something?