All.. well I will be as brief as I can be. After seeing the multiple problems with misfiring that everyone else is having I thought that I might never find the solution to my misfire problem on my 98' f150 2wd 4.6l extended cab. I have just 63,000 miles. After reading tons of posts on advice to fix this misfire code po303 I decided to do the following. I found a guy on ebay, kmansparts, that sells geniune motorcraft parts. I bought plugs and wires shipped for 80.00 thats about 100.00 in savings. I decided I would break down the throttle body and clean. bought 3m tb cleaner safe for sensors and coated TB's as I took apart the TB a bolt to my EGR valve snapped. Finished removing TB, got my torch out and heated and cooled and heated broken bolt, got vise grips out and luckily removed bolt. cleaned TB. I did see some major carbon build up in the 2 small holes leading back to the EGR valve but otherwise it was in great shape. Changed out all my plugs and wires. used a multitester and tested sensors, coil packs, injectors etc. Haynes manual says 6.5-11k ohms is secondary resistance. I saw someone post here 10 -14k ohms is what it should be mine was 13.25k ohms on average. anyway put everything back together also replaced fuel filter, pcv valve and air filter. I had already replaced one coil pack about a month ago from NAPA, so I thought I had the bases covered. Fired it up and it was rumbling like I had a bigger cam in it. I thought well maybe it has to rlearn itself since I had driven it for awhile while it was missing. Went to work the next day and it acted like it might start to run a little better and hey there was no CEL on anymore so I figured until then I will ride it out for another day or 2. Well on the way home The CEL was back so I went down to autozone and now instead of a po303 code I was getting a po302 and po304 code. I went home retested this coil pack, by the way these 2 cylinders run off of the same coil pack and this pack was not the one I had just replaced. Tested pack and now it was reading over 14k ohms. Being the pack rat that I am I kept my old coil pack that I had replaced a month ago that I thought was bad at the time and tested it with my new purchase of a multi-meter and it was within spec. put it on and voila it is ruuning like new again but not sure for how long. It was a pain in the butt, however I was only out about 150.00 instead of about 800= the dealer would have charged to do all that work. I really think I should have splurged and just bought 2 new coil packs as well right from the get go. So, I guess the moral of the story is if you are fighting a misfire that just won't go away. Take a day off work and break it all down. Hunt down the parts cheap and just do it. Plugs, wires, coil packs, air filter pcv valve fuel filter. sensors will give you a different code not a 300+ misfire code at least in my experience that is, but those coil packs, wires and plugs need to just be replaced all at the same time it seems to me. Throttle body Egr passageways will clog so break it on down and just clean it up. Its a lot of work but one day of cussing is better than several days worth of troubleshooting over the span of a month...just my thoughts...