I have a turbo 5.3 and have been going back and fourth with tuner to finalize the tune.. I have a Tial WG set with 13# springs and setup has ALWAYS made 10-10.5 psi with sometimes spiking to 11. Last night I was doing some logs and I got on it twice and it would only hit 9psi max both times just came up to 9 and stayed steady.. I’m no expert but I’m trying to figure out why the drop in pressure all the sudden when nothing’s been changed besides adjusting fueling and whatnot for tune.. we’ve been making adjustments for the last week and no matter what it always came up to 10psi at least. Only thing I’m leaning towards is possibly the “cheap” BOV cracking open under power? But why now and not then?

I have a new spring on the way to eliminate this possibility, and have thought for awhile that it had the wrong spring, as it’s all the way open at idle and Tial states it should only be cracked open and should need 11psi for the -19 to -20 hg my motor pulls in vac.. but none the less it’s always made more boost pressure than currently.

I should note that everything is BRAND new and less than 2 months old EXCEPT BOV.. it’s a Precision 76/75 and Tial 44mm wastegate with an On3 BOV.
Motor is a bone stock 5.3 with BTR springs.

I hope I’m a super rookie and just missing something simple.. haven’t checked thoroughly for exhaust leaks but sure didn’t hear anything while looking it over last night.

I knew the springs rating weren’t set in stone.. especially since I have 13# and only make 10-10.5 lol and I’m not really worried about it power wise cause it still feels the same and runs fine. Just curious as to what could cause it.. never seen it dip below 10. Even on the old On3 turbo it always stayed consistent. I didn’t know if the springs in the gate get tired or if maybe the BOV is leaking off under boost!

Update: after two days of only being able to make 9psi and digging around to see if I could find something.. I decided to change my wastegate springs and go one step higher to see if the psi went up at all. I installed the next spring set (14.5) and tested to only find that I made the exact same... 9psi. Wastegate is new and looked to be in perfect condition while changing springs.

I looked over everything once more, and all seemed to be fine... luckily I had a buddy with me at the shop and decided to have him watch engine bay as I spool’d her up on the brake (yes... he must have trusted me greatly!! LOL) and BOOOM!!! He spotted it right off bat.. one of the silicon couplers on my coldside had popped out partly from under the clamp.. wasn’t even half way off, just a little section on the bottom.. which is the reason I didn’t see or notice when I was looking it over!! Pulled clamp off and fixed coupler and alll is well again!!

Glad it was something stupid!! (ME)