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Ok guys I’m having a boost issue I can’t seem to pinpoint. Truck is a 03 7.3 6 speed bone stock. Problem started as a loud bellow similar to air being blown over a bottle coming from engine bay. from inside the cab it sounds like right where the turbo is, it started intermittently, I could run the truck hard in 2nd and 3rd gear and it would go away and not come back until I dropped to an idle and took off again. When the noise is there, I feel that the truck is missing quite a bit of horsepower and gets terrible mpgs. I assumed with it being intermittent and in cold weather it was the ebpv valve so I installed a pedestal and turbo base that deletes the ebpv, this had no effect on my problem. Fairly quickly after the pedestal install the problem went from being intermittent to nonstop, this was all last winter. I took the truck out of town this summer about 400 miles and a couple hours into the trip the noise stopped, power was great and it stayed like that for about a month then came back on and hasn’t stopped since. In the last week I installed a boost gauge and found that I was only getting about 11 lbs. I found a leaky boot at the spider and decided to replace them all including the intercooler boots. The truck seemed to have a little more power but still only 11 lbs. and the noise. I’ve checked the compressor wheel it seems to be nice and tight and the wastegate arm moves freely. I unplugged the red line that operates the wastegate actuator and see about 16-17 lbs. boost and a little more power (still not normal power) but the howling noise is still there. The noise can be heard at any rpm range while driving but more boost=more noise. I’m not extremely familiar with the 7.3 and I’m hoping someone that is could give me some input before I keep throwing parts at it. Any help is appreciated. Thank you
 

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One thing to look at if you have the ability is to monitor EBP (exhaust back pressure) Excessive back pressure will limit boost - the noise that seems to accompany it is likely a restriction in your exhaust. It is possible for your catalyst to have broken internally and sometimes the substrate can move around and effectively plug the exhaust. I have seen that drive more than one experienced technician crazy. Other than that, being able to monitor the PCM parameters you can not only monitor EBP but see if the PCM is commanding the EBPV closed. Your description of the noise is a little odd though...
 

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How would you go about checking the ebp? The ebpv shouldn’t be a problem since I deleted it. The noise is odd and it’s hard to describe but it’s definitely low pitched and coming from where the turbo is located and it gets louder the farther up in rpms you drive the truck
 

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Did you completely remove the plate and shaft when you deleted it?
DENNY
 

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Check to make sure the 4 bolts between the housings have not fallen out also.
DENNY
 

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You need to make a boost leak detector. You can do this with stuff from any hardware store. Get a rubber boot with a couple of clamps and a 3 inch pvc plug. You'll need to tap this 1/8 NPT and use a male fitting for your air hose. Apply about 15 psi from your air compressor and climb up top and start looking for your leak. Here's what the store bought version of the leak detector looks like - 3" Dieselsite Turbo Boost Leak Detector
 

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You need to make a boost leak detector. You can do this with stuff from any hardware store. Get a rubber boot with a couple of clamps and a 3 inch pvc plug. You'll need to tap this 1/8 NPT and use a male fitting for your air hose. Apply about 15 psi from your air compressor and climb up top and start looking for your leak. Here's what the store bought version of the leak detector looks like - 3" Dieselsite Turbo Boost Leak Detector
I forgot to mention that I had done that in my original post, sorry about that, that’s how I found the leaking boot on the spider, I replaced all the boots and performed the test again and zero leaks that I could find
 

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When you had the turbo off, did you replace the donuts in the up pipes? Could be an exhaust side leak.


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When you had the turbo off, did you replace the donuts in the up pipes? Could be an exhaust side leak.


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I didn’t, I looked them over good and didn’t see any soot so I assumed they weren’t leaking. Is there a way to check them other than looking for soot?
 

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I don't know of any other way. Guess you could pressurize your tailpipe...

Still, you know it's a boost issue. You've eliminated leaks. You've eliminated the EBPV. You really are only left with the exhaust side or an internal turbo issue. If it were me, I'd order the bellowed up pipes and a turbo rebuild kit. I suppose it could still be a weak wastegate controller. I personally dumped the stock controller for the Dieselsite TurboMaster. I can bury my 30 psi boost gauge now.
 
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