my RST has been doing this since I bought it and cant fiqure out what it is! its doing my head in, i've had it in to Well Lane Turbos 2 for it, they were shite charged me for work doing then found the fault was still there.

i've changed the airflow metre, plugs, ECU, removed dump valve, disconnected the cold start valve.

Haven't checked for air leaks, (as i dont know how or where to check)

does yours always do it? mine seems to be in morning mostly (when the cars not been used for a while. for the first 10min then it seems to get a lot better.