Boost Control Issues, falling off at 5500+.

[98TsiAWD]

I have a 50 trim, tial external wastegate, dejontool mbc. There are no exhaust leaks, and no boost leaks.

I am running 23psi, but by 7k rpms that falls to 15-16

My DSMlink logs show the same airflow all the way to redline+ however.

Is it possibly a boost guage issue, or am I actually losing boost?
Im not sure what spring is in the tial, its whatever AGP includes in their kits. I was thinking maybe its not strong enough to hold 23 psi?
The bottom nipple on the wastegate is connected to the MBC, top port is vented to atmosphere.

Any ideas?

 

[92awddsm]

I had the same problem once but it was with a 16g. My intake cam was off 1 tooth and caused boost to fall off early. fixed cam timing and it held boost throughout rpm range.

 

[98TsiAWD]

I had the same problem once but it was with a 16g. My intake cam was off 1 tooth and caused boost to fall off early. fixed cam timing and it held boost throughout rpm range.

hmm, could be a possibility.

When I first started the car after the rebuild I set the timing to 5 degrees BTDC. Then about 3 weeks ago I was trying to tune the car and could not get rid of knock no matter what I did and was getting about 4-5 degrees timing at WOT.
Then I checked the timing and it was 15 degrees BTDC, wtf. So I reset that and went and tuned with no problems at all. And Im pretty sure I was holding 23psi all the way to 8k.

But now I noticed its falling off, but it might have always been doing that and I never noticed.

I guess Ill pull the timing side apart thursday night and check it out, really hoping it didtn jump a tooth.