My 1998 chevy silverado 2wd 5.7 liter, has very recently had an issue of stumbling when accelerating. It happens at when the truck is in park and I hit gas itll jump up to 1500 then drop to 1300 rpm for a moemnt before normally reving up. the problem also occurs at or above 70mph it will have the same exact sympton. aany suggestions on where to start looking or what the problem could be?

 

Likely a fuel system issue. I'd run some Chevron Techron or Lucas Fuel Injection cleaner down the tank (They both contain PEA) and find a safe road to do an "Italian tune-up" on and floor-board her hard.