Guys got a small boost leak. Had my car the rollers yesterday found that it peaks at 1.3 then tails to under 1.1 as the revs goes up. It was mapped fair few years ago to 1.3 by powerstation. Made 332hp but yesterday made 300.2 so how would I find such a small leak. Car is 02 sti bug type uk

 

You can buy leak testers online, just need a silicone blank and a compressor, then listen for the high pitched whistle under pressure and you'll find your leak. You could also get it smoke tested by a local garage, usually quite cheap and gives brilliant results