How did you check for air leaks? I only ask because they can be really hard to find I use brake cleaner and spray it over the engine bay or anywhere there could be a leak and it the engine tune changes means theres a leak and you can locate them so much easier, also does it have an idle control valve? As they can get clogged up and need cleaning out there's a how to guide on the guide section I've done it myself good guide, I've got a rs turbo so not to familiar with 1.3 set up