2002 Chevy s10 misfire

When having to accellerate hard or drive up-hill while
accelerating my service engine soon light will flash. It has
been doing this ever since I've bought the truck. It is a 2002,
6 cyl 3.4L with only 94,000 on it, I purchased it a couple
years ago at 60,000 and since then have been using it for
camping and traveling. It seems grossly underpowered
when traveling uphill. Fully floored on flat land it can reach
up to 85-90 before the engine light flashes. When going
uphill and fully floored it maxes out at 50 mph, even with a
light payload the light will flash and my engine will start
sputtering. The code it displays is a p0300, random misfire.

I first changed my spark plugs and distributor cap and
rotor. I received the same troublr code not long after
making those changes. I then changed Spark plug wires
and spark plugs yet again thinking i had a fouled spark
plug. Then I did a fuel pressure test and found i had a fuel
pump beginning to fail. I replaced that with an OE pump,
went to the mountains and yet again got the code and light.
I then replaced my distributor cap and rotor again and then
also replaced the intake manifold gasket. Still got the code.
Intermittently between the multiple p0300 codes I would
get a p0304, spark plug #4 misfiring. I switched spark plug
#4 and #1 to see if it would give me a p0301, but instead it
returned the same code, p0304. I am thinking it may be
distributor itself going out but would like some input before
changing anything else.