2002 4.3 misfires at above idle

I have a high mileage (250k) 4.3 in a Silverado that has nor ran right since I've gotten it. Its a 5 speed. It idles fine, but while going through the gears, once you reach about 1800 rpm's, it seems to misfire and sputter. Sometimes this happens sooner in the rpm range, sometimes higher. Sometimes it doesn't happen hardly at all. Definitely sounds like ignition. The previous owner said he replaced the cap and rotor (I can verify the new cap, haven't pulled it to see rotor condition), and I installed new plugs and wires. No codes. Any suggestions would be appreciated.

check timing, fuel pressure

I had the same problem and it was because of a cheap cap and rotor from autozone I went and bought an oem set and it fixed it

Sounds like worn distributor gear. Thise are bad about it i would replace the whole distributor