Distributor cap rotor

First you can not put Bosch plugs in it. Also watch cheap wires from parts house. Also check fuel pump pressure at high speed. Also watch for Catt converter plugging. Try unscrewing up stream o2 on both sides then drive. If goes away plugged Catt. You can scan those and see fuel values. Then you can tell. Any codes?

What about Distributor cap & rotor?

With only that information, I'd first look at or replace the fuel filter.

TUNE-UP, SPARK PLUGS, WIRES, AIR & FUEL FILTERS, FUEL INJECTOR CLEANER IN TANK, ALSO REPLACE PCV VALVE, & MOST IMPORTANT, REPLACE EGR VALVE, IT GETS TOTALLY CLOGED UP, YOUR ENGINE IS KNOWN FOR THAT. I HAVE A GNC 2500, 3/4 TON. SEEN IT ALL. CHANGE YOUR DISTRIBUTOR CAP & ROTOR ALSO. JUST DO IT !!!!!!!!!!!

Recheck your firing order for basics. If this is in good, a compression test may be necessary. Which enigine do you have?

CLOGGED FUEL FILTER OR CLOGGED FUEL INJECTORS.WILL CAUSE SPUTTERING AND MISFIRE.LEAKING EGR VALVE WILL CAUSE ROUGH IDLING SPUTTERING.

it sounds like this didn`t happen until you replaced these items.i would recheck the firing order and make sure the wires are on the distributor cap correctly and in the order the rotor turns

start at the distributor and look inside at the posts. if they look wet or damp then spray it down with WD-40. it displaces water. if the posts look dirty or corroded then you need a new cap and rotor.
plugs may need changed and wires may need changed. another possibility is a coil may be giving you problems. but the worst case may be that a injector may be bad. do the simple things first then proceed to the injector checks. you will have to take it to a shop for that.

have you checked the injectors? might be the problem.

Sounds like moisture is getting into the distributor cap. Try putting a thin film of petrolium jelly around the lip of the distributor cap where it seals down onto the distributor. This should stop the water from getting in.