2wd and 4x4 both got only 1 pickup pipe......try taking the dizzy out and get a cordless drill with a socket on the end and spin the oil pump manualy so you don't fuck the engine(i had to use 1 of them flexy end things ....sounds to me if you have checked everything else i would say you have got a doggy pressure releive valveif you have not got the standard spring to put in to try it i have one i could post to you........hope you get it sorted mine has been mint since i put 2wd pickup pipe and pump in......