missfire problem

[20''strong]

i had misfire code,maf and bank one lean i changed plugs,plug wires and intake gasket after i found it leaking.all codes went away except for the random multiple miss fire.would a exhaust manifold leak throw this code?code is p0300 if that helps anybody,

[Tank]

shouldn't. but could. i'd look at o2 sensors. then say you can clean around mouth of TB. then other things are MAS and coil packs

[20''strong]

I replaced my upstream o2's,cleaned my trottle body and replaced my maf with one i had off another motor.I checked fuel pressure and fp regulater all checked out fine.im outa ideas.