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I have a 2002 Chevy 2500hd lb7 duramax (on my phone and can’t fill out the sig) efi live tuned by ridge runner, stock trainer, banks wastegate, new cp3 with less than a couple thousand on it. Injectors were pulled and rebuilt when I bought the truck two years ago.
It started august of 2018 when my truck got hot while towing my camper, motor and tranny got between 215-230. When we got home and realized the inter cooler lines were tightened all the way snug which probably cause my problem. Within a week I blew the bottom tranny line on the freeway and had to get towed back home. But my the time we got home I think the tranny way about out of fluid. Refilled it and went on but now fast forward from that point, the truck Has a hard time building boost under 2000 rpms, once it hits about that 2000 rpm range it takes off and throws you back in the seat. I’ve checked boost lines, replaced cp3 thinking that might be the problem, added a fass lift pump. I don’t want to throw any more money at things that aren’t working. The last thing I can think of is maybe bad MAF sensor but I’ve pulled it out and cleaned it 3-4 times since August 2018. Any help is appreciated
 

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Checked for any codes?
 

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Checked for codes with nothing pending or setting off check engine light.
 

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I have an edge CTS 2 monitor and when checking the engine load at idle is about 25-35%
 

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When was the last time you changed the fuel filter and air filter? Any smoke? Stock air filter? Does this on all levels? Have you date logged to see what’s going on? What does ridge runner say?
https://www.dieselplace.com/forum/63-gm-diesel-engines/7-duramax-first-generation-2001-2004-lb7/616321-no-low-end-power.html
https://www.dieselplace.com/forum/63-gm-diesel-engines/7-duramax-first-generation-2001-2004-lb7/546722-2003-lb7-loss-low-end-power.html
Google (Duramax Lb7 no low end power) lots of info. Maybe you’ll find something.
 

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20 lbs of boost at wide open throttle getting on the freeway. As soon as the torque converter locks in 5th gear the boost goes from 15-20 down to less than 5 in a matter of 2 seconds. No smoke, as I turn up the tuning it gets even more bogged down and sluggish on the low end but spools the turbo a lot quicker once it’s gets into that higher rpm range. Fuel filter a couple months ago and less than 5k miles on it. Changed it in hopes it would help reading so many people mentioning it but no help. Air filter about a year ago. I will try to change that. Ridge runner made me sent them wot throttle pulls. I was thinking it was the cp3. They thought it was the wastegate. Replaced it with a banks wastegate and set to about 7 turns. I’ve never heard a good number for how much turns/preload to set on it for everyday driving.
At about 65 on the freeway I’m at about 0-2 lbs of boost maybe. I have to give it about half throttle to even get it to move. Even at that once I’m driving I can only get about 5 lbs while trying to increase speed. If I floor it it spools the turbo quick but doesn’t shift down and as soon as I let off the gas peddle it’s like I loose all the momentum and boost I just built.
 
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