Originally Posted by Terry@BMS
Hmmm, that is a bummer. If we could get a direct reading of pressure we can narrow it down. Same thing happened to the other link I posted with the other guy. Spooled super quick, held low boost wouldn't go more and would drop by redline. Just like your logs show us. He tried a bigger AR exhaust housing, still didn't do the trick. It lowered the back pressure from 3:1 to 2:5:1. He then changed the turbine wheel with that AR housing and bam. Back pressure when down to 1:1 low rpm then mid range and top end was 2:1 which is pretty much right on the money.
Tuning can only do so much, the turbo is spooling. There is something else that's not letting it do it's job. I wish I was more familiar to JB4 logs, but it's not as descriptive as my HPTuners was so I can't go further into the details of information of what's exactly happening. "