98 Blazer - runs rough and loses power

Hi.I have a 98 Chevy S10 blazer with 175K on the 4.3L 4 x 4 engine. I stared out a couple of months ago with my blazer hesitating when I stepped on the gas, then it proceeded to start backfiring & finally it would not go anywhere when the accelerator was pressed. Was throwing a multiple cylinger misfire code when tested. I replaced the distributor cap & rotor, spark plugs & wires, EGR valve, etc and no luck. Towed it to the mechanic and he said it was the fuel injection system & possibly the Cat converter. Replaced both along with the fuel filter (both looked horribly clogged) and it runs better, but still not enough for me to drive it on a regular basis. Still has trouble getting out of it's own way when you press on the gas (especially uphill) and the check engine light is back on & flashing. Also continues to backfire intermittently. Engine sounds good (no knocks but runs better when cold than when it warms up. Any ideas? Please help.I just want to be able to drive my truck again.=) Thanks so much!