power surge
 

My 2001 wrx bugeye with a ppp has never been 100% crisp and smooth. Now it does not come into life until it hits 5000 rpm. It does not have a missfire but once it hits 5k its like switching a fourth cylinder on. Its also quite thirsty. 20 mpg driving steady. I would expect about 25 mpg. How good are scooby clinic in Chesterfield?

Scooby clinic have a good reputation.

It maybe a leak somewhere, boost? intercooler pipes?