Dtc P0300 & P0304

OK, I know that each DTC points to an engine misfire but I can't find any problems. It a 98 Pontiac Transport with 172K miles with an intermittent rough idle. I've changed within the last year, plugs, wires, PCV, O2 sensor, cleaned the TB, MAS, and the other thingy that has the printle (what ever its called). No vacuum leaks that I can find. Swapped coil paks also, Still no joy. :(
Anybody else have this problem and fix it? Now the other thing I have is the brake/turn signal issue with the poor connection. Could that be part of it somehow?

Could be a couple of bad fuel injectors or a bad coil pack.What brand plugs did you put in?If you put in Bosch,throw them away in the garbage can and put in AC Delcos.Bosch plugs are the worst plugs to put in a GM and GMs run like crap with Bosch plugs.

I'll have to look what I installed. Just looked at my records and I installed plugs 25K miles ago. They just might be toast already, damn feels like I just replaced them.
I know I just pulled plug #4 and it looked good. We'll have another look tomorrow.

Just checked the plugs (why so early?) they are Bosch platinums. :( I'm going to swap them out with the OEMAC 41-940 about $6 a plug. I've got my fingers crossed this does.
I hear about a lot of vehicles having problems with Bosch plugs.

Looks/feels like the AC OEM's did the trick. Now all I need to do is clear the codes and get it inspected. I'm only 5 months late. :)

I can manually clear them with my auto tap but then I'll need to drive it until it does all its checks. Any other way to clear the codes. How many drives cycles does it take?

Van is running better than ever. :) All codes cleared except P0420 and that'll probably clear after auto-rx has had some more time to clean up the engine.

A note for anyone with a GM product: DON"T USE BOSCH PLATINUM PLUGS!!