Its on a my00 classic with scoobysport bb, centre decat, sti v5 tmic, k&n replacement filter element, turbosmart mbc. It made 260bhp on the powerstation rollers at 12psi boost. I have a boost gauge but no afr or knocklink.

The problem is that whenever i try to crank the boost up above 12psi the boost seems to be cut off when i get upto around 3500rpm - 4000rpm. I don't think its the boost fuel cut cause thats around 17psi and i'm nowhere near that. Could it be the ecu sensing det and cutting the fuel for that reason? I thought my00 cars ran rich so could take slightly higher boost? It has a ae802 ecu, i don't know whether its been tek'ed or not. i've done alot of searches and not really come accross anything like this?