stuck in amerillo

we have replaced the lpop dummy plugs starter turbo stc kit standpipes crank sensor cam sensor no codes presser is good aroun 800 after about 15 mins it just drops when you slow down someone says the fins are pressed on on the hpop and that will make the presure drop on the injectors? ficum is reading corectly they had the hpop out and siad it looked fine they used a wix filter ?:4-dontknow::4-dontknow:can a truck start and run fine and then just quit when you slow down some one said it could be the hpops vain slipping when they get hot is that possible at all ? are their gasket we are missing they did a pressure test and found a leak in the driver side stand pipe but nothing in the injectors please help any advise has anyone heard of this