hey guys I am havin an issue with my 99 7.3 powerstroke. I need some advice. It starts and idles fine but after four or five miles on the highway it starts to stall. sounds like it's losing fuel. I shudders real hard loses speed. I can hear the injectors knockin and I get some erractic shifts. the truck has 156,000 miles a hypertec tuner and a bullydog moniter. codes include a p1211 ICP pressure +/- desired value. I know number 5 injector is leaking but it has been leaking for almost a year. this symptom is 3 days old. There is a code for EBP but with scantool connected back pressure is 15-28 at all times. I heard it could be the sensor tube clogged. but Dont think that is my problem. During stall I cannot tell that any live data is being disrupted. my injector pressure still reaches 3000psi. My bullydog monitor indicates no loss of boost and no extreme exhaust temps. I have replaced the fuel filter, air filter, and changed the oil. I have also pulled the fuel tank and it is clean. no obvious diesel leaks. oil pressure is normal.

I'm thinkin a lift pump may be goin bad but am reluctant to start throwin money at this problem. Am I lookin in the right direction or am I missing something simple.. any help would be greatly appreciated

thanks poorboypowerstroke