5.7 missing under load. Out of ideas..HELP

Anyone please feel free to point me in an area I have not been. I have a 98 Silverado 5.7 that misses and skips going up a hill under load or if you get halfway up the hill, back off the pedal and then gently press the gas pedal again to resume. I have had the fuel pump replaced within the last year, put a new filter in today. Idle PSI is 53, while driving under the failing condition it is around 58 PSI. The injectors were changed to the MFI from CSFI last December. The plugs. wires, rotor button, dist cap and coil have been replaced. MPG is 16 city. around 19.5 on the Hwy. If the hill is step and long enough I get the generic P0300, random misfire code. The condition is starting to get worse ( easier to produce the failure ) so I need to get busy. Thanks for any Ideas. :screwy:

So hows the fuel pressure key on engine off? Does it hold the pressure after the pump shuts off? If it doesn't hold pressure after the pump shuts off, crimp the return line, there is a section of hose near the fuel filter, and see if the pressure holds steady when the pump shuts off.

It holds around 53-55 for at least an hour.
Tks Steve

Do you have a scantool? If you do see if it will show a value for cam retard or camshaft offset- it should be 0 degrees, the engine needs to be over 1000 rpms for the value to be accurate

No scan tool, I have been looking for an Auto Xray on eBay. a 4000 or 5000. I don't think the cheap one Auto zone uses can read anything but DTC's. Thanks for the reply.

Unless Auto Xray does an update, you won't be able to find what the cam retard is on a 98 with one of their units. I have the 6000 and I have heard from people who still have the EZ-Link 2 line units and they have no luck either

Just a thought> could it be a intake gasket i sure have been reading alot about these newer trucks that have bad ones?

I replaced the intake gasket last year, $40 and 8 hr of my time. A better deal than $650 at the dealer or $550 at independent shops. No air leaks,etc as I can spray all aorund the upper intake with starting fluids and no increase in revs etc. Thanks for the update on the scanner. It may be cheaper to let dealer diagnose this one and go from there. Man that is a scary thought me saying that!