1jz single turbo low boost and surging

[toy4speed]

My Mk2 Supra was running fine last year, sat during the winter months, now I have an issue that just puzzles me. Maybe others can offer some info.

1jz, gt30 single turbo, tial mvs 38mm WG, tial bov. I used to get good throttle response at 3k rpm, pulled strong up to 7k and smooth. This year there is no power below
4k rpm, boost comes on, maxes at about 18 psi, and engine surges at full throttle at 5k to 6k rpm. Last year I was easily getting 21 psi of boost, using my tru-boost ebc.
Despite changing settings on the ebc, boost is still nil under 4k and won't go over 18 psi. Intercooler pipes and couplers look good. All the parts were new last year.

Hard for me to fathom, but I'm thinking the WG is kinda stuck open. I am getting some boost, it just comes late, and not as much as before.

Any thoughts much appreciated!

 

[525gte]

I was also thinking wg or fueling issues.. what are the afrs when this happens

 

[toy4speed]

In the 3k to 4k rpm range when throttle response is now sluggish, not much pep at all, the afr has been around 11.5 to 12. Since I wasn't getting any boost down there, I leaned out the fuel settings in that area so its more like 12-12.5 afr. I also tried bumping up the ignition advance in that range, again hoping to get some of the low end power back. No improvement.

On the upper end, 5k to 6k rpm at full throttle, the engine surging occurs but the afr was in the 11.5 range. About where I tried to keep my settings on boost.

I also tried driving the car on the freeway today, 4th gear at 3k rpm going slightly uphill. A good opportunity to floor it and see what kind of boost I could develop. From 3k-4k rpm, I saw about 2-3 psi boost. Didn't start to build till after 4k rpm. I'm thinking either I have a heck of a boost leak somewhere, or the WG is bleeding a bunch of exhaust flow. I suspect the WG somewhat mostly because I have tried to increase the boost via the Tru-boost ebc, and max boost really isn't going up. I guess that could occur via a boost leak somewhere in the intake too.

Other thoughts I had was maybe a leak at the vacuum line going to my heater controls, but I capped that line and so no improvement. Perhaps I could be losing boost via the power brake booster, but seems very unlikely. I have an extra check valve, I could put it in-line to test.

The motor tests at about 190 psi compression across all 6 cylinders. Honestly, that surprised me for a turbo motor. It would seem that with that kind of compression, even with no boost, the low end grunt should be better, but I'm kind of a noob with FI motors.