Help! Need Ani Helpful Advice

[mwin]

i drive a series 2 none turbo r33, n recently its been playing up on me, wen i cruise from gear 1 2 and 3 (sometimes even 4 and 5) da exhaust pops, as if its coughing, causin da car to lag/back fire slightly,

eg. it would puff 3 times on 3rd gear and den cruise nicely after. can anione tell me wats wrong wit it?

im gona have it majorly serviced as soon as possible. but ide feel better knowing wat causing this.

cheers for ani help

mike