Ford Repair: rough idle 2002 mazda b4000 code p0304, vacuum leak, mazda b4000

Question
Trouble code P0304, swapped #4 plug with #5 no change. No miss while on highway but misses while idling. Found one vacuum leak and replaced pipe and elbow. 156000km on truck, seems to ping more under acceleration than it did before this code. What should I look for next? Thanks

Answer
hey there. a p0304 code is a cylinder 4 misfire code, so you are on the right track. make sure the coil pack is firing the plug and make sure the fuel injector is pulsing, if theses are ok then do a ompression test to see if there is enough compression in that cylinder. let me know after you check these, talk soon
Chris P