I have a 96 1.8t sport a4 which has been chipped to 230bhp. Its got a decat pipe + mongoose exhaust. Since its been chipped the power below 3000rpm is very lumpy. Its seems to come on to boost then go off. It does this at about 2800rpm ithink, the next time the boost comes in its fine up to the redline.Its very noticeable and quite annoying. Any ideas?