Police pkg Hemi misfire and Overheating

I'm having issues with the 5.7.Have occasional misfire and also it gets hot and usually runs a little hot..Just replaced water pump and it's still doin it..I think it's a wiring issues or sensor..The only codes that pops up is misfire in cyl 6.Also I get white buildup on three or four sparkplugs...u just replaced water pump and checked all plugs..Also have slight smell in exhaust but can't tell if it is rotten egg smell..I wanna perform test on catalytic if possible.Also gonna check n see if radiator is clogged..I'm hoping it's not blown head cause can't afford that one..Anyone have any info or suggestions..