hello im new in here but i need help with my 4.3 was running fine 205000 miles started it up one morning and it had bad miss, put new plugs ,wires,rotor and cap nothing helped checked egr valve , all old plugs on left bank were sooted right side were white any suggestions

With one bank black, and the other fine, that kind of makes me think a exhaust restriction. Do you have duel cats?

if its like the trucks it should be a tbi, with one cat. im thinkin intake gasket. try spraying carb cleaner around where the intake meets the heads with the engine running and see if the pitch changes, if so it needs gaskets

thanks for your input the complete exhaust system is less than month old and spraying around heads with carb cleaner and at vacum points has no effect thanks again

Did you have it scanned for DTC'*?

only code was o2 sensor will have new one here 2nite

which code was it, if it was rich or lean it could give better indication of what the miss is.

He could have 4 codes just on that one o2 sensor. 2 of them would have nothing to do with the sensor itself.
bank running rich
bank running lean
o2 #1 slow response
02 #1 reading over limits. (this one I have seen myself. the sensor is reading over 950millivolts when it shouldn't be).

well put new o2 sensor on and still have a miss and no check engine light has come back on yet

You may have a bad injector. It is not uncommon in that vintage 4.3.