I have an 02 vrs with 80K on the clock. it has forge DV and stage one chip (all done by previous owner). just this week it has lost power. it is still driveable but it is as if the turbo is not kicking in as strong as it has in the past, the turbo is still working as i can here the DV blowing off. if i turn the ignition on and off, it goes back to full power with a very strong turbo and boost.

any thoughts?

Is the engine management light on when its low on power?

Could be overboosting and going into limp mode. Do you know who mapped the car? Also, as RAF said, is the engine management light on?