Loss of rail pressure @ WOT
 

I have googled and found nothing exactly like my issue. I have an H&S MM with hot tunes programmed with the overdrive unlocked on my 2011 ram 2500. Have all deletes. Even took the disk out of the intake. While in performance if I stomp on it I will build to around 17K or so rail pressure then fall off to 4K. The lower power level I run the higher I can build before it falls on its face. I also have a Snapon Solus Ultra and have manually toggled the lift pump and it turns on and off. I do not have a gauge on the fuel supply line. Just changed the fuel filter. Just cleaned the MAP and MAF sensors. Same response. Rail is plugged and just installed a new plug as I am out of town on a rig and is cheaper to replace a plug then to buy a new relief (old one is at home). I can performed cylinder cutouts to no avail. I did show at one time a code for basically loss of boost and checked all boots and clamps. This is when I cleaned the MAP and MAF and cleared and hasn't come back. My question is, since the problem gets worse on the higher performance levels could the screen on the in tank lift pump be clogged allowing flow but not enough for high demands? I get a lot of black smoke as well when this happens.

One last thing I build boost just fine until the rail pressure falls off then it drops as well.

Sorry been a while I didn't realize I had my truck with adds in the signature. Only thing different is I don't have the TS plug and play. Just the H&S. Anyone have any ideas? I kind of have my mind made up to drop my tank and check the fuel pump for clogged screen/cracked or separated fuel line. Just seems like it cant get the fuel it needs once the demand goes up since it gets worse the higher the power setting I go.

mine was doing this as well until i got a aftermarket lift pump installed. I went with the FASS 150 and havent had problem since

I'm having a similar issue but my tail pressure is fine. I have noticed my boost holing low

I fixed it a while back but never posted because no one else did. I dropped the tank and the suction on the fuel pump was completely clogged. Cleaned it all up, reassembled, and filled up and no problems since. My rail is plugged and has been since 6000 miles when all the emissions crap fell off. No problems with any of that. The suction was my main suspect from the beginning but it was also the most labor intensive so I didn't want to do it until I had to. Main hint was it would get dramatically worse and or die when it got between half and quarter tank when the fuel could no longer fall in the bowl and it had to suck through the bottom that was completely clogged.
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If you have a check engine light in willing to bet you have a major boost leak. It would be hard to hear if you have an open cold air intake while driving though. Check all boots and inter cooler. Also could be the exhaust brake sticking if you never use it. Start turning it on every time you drive it to make sure it stays free. Hard to diagnose without live data or codes...

I would also, for shits and giggles, pull the MAF by the air filter and MAP on the back of the intake horn if I remember correctly and clean them with Electra clean or I think they make a cleaner for them. I always use Electra clean and never had a issue.