not trying to be a cop out but any reason (besides cost i guess) you wouldnt just want to replace it with a Link? i did the same thing with my RS primarily because i got sick of all the CELs haha. Also slightly related, are you still running the old school coil packs? One thing that solved a number of 'gremlins' was going to the newer style coilpacks and deleting the old ignitor. 

the boost gauge i believe is the clear yellowy line T-ing off from the BOV nipple with that big red tube i will at some point this week take the secondary downpipe off and let it idle to see if any exhaust gasses get past, does that seem like a reasonable way to check ?

If your bov is making reasonable volume then the intercooler and all the way to intake is likely good. is the boost garage sharing a line with the bov, or is it off something else?   have you checked the exhaust valve to the secondary turbo isn’t always open?        

I checked the car park for any fresh oil patches.

hey all, i've got what i believe to be a boost leak on the primary turbo in my '02 B4 car starts, idles and drives fine but i can't manage to push the primary above 3-4psi - according to my boost gauge at least (at idle it reads -1psi)   when i give her a run for her money up a hill she hesitates a fair bit during the VOD but when the secondary kicks in she really goes (my boost gauge still doesn't move above 3psi but the BOV goes off so it's definitely above that), so as far as i'm aware that would mean the differential pressure sensors and boost solenoids are fine and the secondary is healthy. i've read online that the turbo's on these cars are meant to be pretty quiet, but i definitely hear spool or whistling of sort when driving.   i did buy this car with a bad head gasket and had the engine in pieces for a few months but i've been over the engine bay several times confirming all my piping goes to the correct spots and everything looks fine, though i haven't opened the BBoD yet - all my restrictor pills seem to be in place aswell. there is some shoddy piping around the turbosmart BOV the car came with and the boost gauge tubing (ill attach a photo) - if it means anything ive pulled these pipes off and none of them seem to leak air - but i dont think these are much of an issue (probably not good to keep them though).   i've read a bunch of different forum posts and my best bets right now are relating to the intercooler, intercooler piping or ECV (i do hear the ECV rattle during the VOD changeover) and i'm just not sure where to go from here. visually the turbo -> intercooler pipes are, well, worn, they're not the best and have signs of use but no visible holes or cuts that would leak out air. the clamps themselves are working and tight and ironically the only one of concern for me is on the secondary turbo. it's possible that the metal pipes from the turbos to intercooler aren't on fully tight aswell as we had a MASSIVE boost leak a month or so ago that was from the secondary side one not being on properly.   so essentially to sum up my issue; car lacks power on primary, boost gauge won't show above 4psi, won't activate BOV plenty of power of secondary, boost gauge stays at 3psi, activates BOV ECV rattles during VOD and car surges (opening ECV, dropping boost, closing ECV, gaining boost, i assume)   has anyone had a similar issue before and can give me some insight into what this could be ? are these symptoms all pointing to a particular thing ? forgive me if im being slow haha this is the first turbo car i've owned thank you's🙏   BOV / boost gauge piping below