I have a 98 Suburban 5.7, after about 10-15 miles it starts loosing power, gets worse under throttle, until it barely runs, can stop for 15 mins, runs good for another 10-15 miles. get code 131 & 151; cats, o2s changed, fuel pump replaced about 7 months before problem started; replaced air plenum gasket, ran about 50 miles & started doing same thing; fuel pressure is about 52, but remains the same when acts up. any thoughts? scratching my head here! fuel filter chaged too

 

Welcome to the forum.

First thing I'd check is fuel filter. Even tho pressure seems OK, a clogged filter will kill flow. Not sure what the codes are for.

 

what shape are the injectors in? have they been cleaned or replaced you could try a couple of bottles of Techron and see if performance changes

 

You are still getting O2 codes after replacing them. Check the wiring all the way up.

 

my tahoe does the same thing, turn off and restart and works fine for about 10 min then starts acting up again.
did you locate your problem

 

not yet, replaced air plenum gasket & ran alot farther, but started doing it again. several people have told me it sounds like the fuel pump, it's supposeto have 60-65lbs of pressure, it's putting out about 52, but it never drops when it acts up. ordered an oem pump, waiting for that right now.

 

its the fuel reg located inside of your block. it is a little diaphram that sits to help boost the fuel pressure at the injectors. if it goes, kiss all your fuel pressure good by at the injectors. i do recommend you take it in to have a mechanic replace this part though due to its location and check the fuel pump again. when my reg broke on my 97 burb it took out the fuel pump as well. just a thought

 

replaced fuel pump with oem pump and it's been running fine since, hope this helps you.