In my quest to eliminate any possible causes of weird knock I've been getting at stage I, I wanted to try and do a boost leak test. I've seen all the threads for how to build a tester and what lines to close off first, but since the 5th gen turbo is underneath and the turbo intake is routed under the engine internals, any ideas for the easiest way to do this test without damaging anything?
One of the reasons I want to do this is that in my logging my A/F learning numbers, while not over +5%, are almost always hovering right around there and have never been negative or zero. Before my car was even having issues with the DAM not rising to 1, I sprayed the MAF with MAF cleaner and replaced the Purolator replacement air filter with the OEM filter and the DAM routinely comes up to 1 now. The MAF looked spotless before, so I think the filter wasn't sealing properly. But after a lot of driving, my long term fuel trims have stayed on the positive side. fahr-side, who's knowledge of this platform I respect a lot, has said before that even though Cobb says that +5 trims are OK, these cars are generally set up from the factory to have a zero to -5 trim if everything mechanical is sound. Also my boost has been generally peaking at 13.5-14 rather than the requested 15 for the 91 OTS map.
Its for these reasons that I feel I may have a subtle intake tract issue, which could also explain the knock at low-mid loads at highway speed under mid throttle. An intake leak could lean out in these no-low boost areas, but then could still be OK under WOT conditions. Any thoughts on this logic?