bad misfire?

I have a 99 gtp, and it started acting really weird the other day. I've dealt with missfireing is this car alot, but this time its alot different. I happens when im accelerating and just cruising not giving it any more throttle. The car seems to drop rpm's out of nowhere it doesn't jump around like its done before, if i let off the gas then push it again most of the time it still does it. I had the car scanned and the guy told me it was probably a wire or plug, so i replaced the coil packs, that didn't fix it so i did the plugs and wire, which are only 5000 miles old. the scanner said that 1,2 and 4 were missing. If anyone knows what the next step would be i would greatly appreciate it. Also it isn't giving me a ses at all.

I got to reading another thread on here and seen that the o2 could cause this, so i went and changed that and its done it once since then, but i was thinking that maybe unplugging the battery for the night might reset everything and fix the problem now that those things have been replaced.