I had my car RR'd atyesterday and it's making okay power, about as much as expected but the way the torque is delivered is very strange. It comes in strong at 2,000rpm but after that it is very up and down before dropping off at around 4,500rpm. The power is delivered constant and looks good apart from a small dip just after 4,000rpm.
The operator said it looked like it had an airflow problem and asked what filter I had. I have a K&N panel. Is there anything else that can cause this, as I always thought that the K&N panels were quite good?