1998 C1500 silverado 5.7L misfire

My truck started to misfire out of nowhere. Limped it to my fathers house so we can have a look. short term fuel trims on bank 1 were just fine, bank 2 side were awful at -30.5%. long term fuel trims on both sides were between 10-18% (cannot remember +\-). checked everything except for noid light testing. will attach notes on tests. everything on ignition side looks satisfactory. i had grey smoke that reeked of fuel coming from my bank 2 exhaust pipe. fuel injectors were checked for leakage but they did not leak. fuel pressure regulator also does not leak. compression was great. sparkplugs 2 4 and 6 had sooty residue, sparkplug 4 smelled of fuel. sparkplug 8 looked fine. bank 1 side plugs were satisfactory. distributor cap and rotor had no issues. 
only problems dad and i found that COULD have been the issue was some oil around the base of distributor and some inside the intake manifold. 
 

fuel trims on bank 1 were just fine, bank 2 side were awful at -30.5%. long term fuel trims on both sides were between 10-18% (cannot remember +\-)

One possible cause of a bank-to-bank fuel trim imbalance can be a restricted exhaust. The bank that has the restriction will be RICH, causing fuel trims to go negative. I would pull the Upstream O2 sensor on Bank 2 and install a pressure gauge. Exhaust back pressure should be less than 3 psi, at steady 3000 RPM. I like to see 1.5 psi, or less. Anything over 3 psi is a concern.

yes , that is good advice from Chad if that does not work and o2 sensor work good . you might want to check compression on that bank , might have a broken valve spring