Hi everyone,
I need some help finding out what is causing low boost on a 2007 F550. The owner put in a 2003 turbo with a VGT solenoid from his old 2007 turbo about a month ago, replaced the VGT electrical plug because the old one was frayed, and then took the truck to a Ford dealer to have all 8 injectors replaced. After 50 miles he complained about low power and no boost so I found it was 10 quarts low on oil and I decided to clean the EBP tube at the same time (I offered to also clean and inspect the turbo but he disagreed because he said it was just cleaned). That seemed to cure all problems (except a cylinder #8 contribution code that I believe is unrelated to the low boost problem) so I drove the truck 70 miles back to the owner's house. Since then it sat for a week and he drove it 50 miles today and complained about low boost again and said it would only build 4 psi at WOT. I told him to pull over and unplug the VGT and listen for a different pitch in the exhaust tone and he said there was a definite change meaning that it likely isn't a bad VGT solenoid or stuck vanes. Does anyone have any idea what could be wrong?? The owner thought it was somehow related to cruise control but I don't know how that could be related.

some background info on the truck: 2007 F550 w/ 200k miles, EGR delete, new CAC boots and metal cold side pipe

Thanks, and sorry for the LOOONG read!

 

I would check ypipe for a leak.

 

I tried to check while I had it and didn't see any obviously massive leak but what had me confused is to why it came with a low boost problem, was working perfectly for 100 miles, and then would have the low boost problem again

 

Stuck egr valve will do it.

 

With an EGR delete, though?

 

MAP sensor hose disconnected?

 

I'm putting another turbo in mine because of the same problem. Compressor side was grinding enough to keep it from spooling but thank God not enough to gernade it. So now doing a Powermaxx, gauges and s and b intake as my turbo was also dusted due to the junk afe that was on there