I have a 2001 Ford F-150 4.2L V6 standard transmission with over 200,000 miles on it. I've been getting the codes P0304 305 and 306. When i changed the spark plugs and wires out I noticed there was oil in cylinder 5.... I was also having issues with the catalytic converter..I guess it is breaking inside and shooting parts out to my muffler... Well I cut the cat off and attempted to unclog it and put it back on... Would i be better off just leaving it off? Or putting a straight pipe in its place??? I had thought that cleaning it a bit might clear the codes... but I was wrong... So i got to researching on the cause of the oil in the spark plug... Could that be causing error codes in all the cylinders??  (4,5,6)     Also there was some black gunk on the plugs when i checked them today... What is that from??  Im about to go buy a new gasket and grommets... Is there anything else I should try to get? Or any other ideas of what it might be before I go spend money?? 

                                                         Thank you

Also, at some point it was also throwing out the codesC2B10, C016b, and C0703...Anyone know what those are ??? 

Current codes: 

P1043

P1151

P0305

P0304

P0306

P0172

P0174