Bad exhaust smoke

where do i start.....ok bought car from auction that was my first mistake it had a misfire i stripped head and found broken exhaust valve i replaced valve and rebuilt using new gaskets and head bolts started it up sounded great as it got warm started to smoke black/blue so stripped again put full set of oil stem seals in and lapped all valves just to be on the safe side rebuilt again new gaskets/bolts correct touque....new plugs, new air filter, engine flush then oil & filter change....rechecked cam timing using TDC on 1 that was spot on...started engine smoked when hot realy bad again so did a compression test all 4 cyl within 3 psi of each other...did a leakdown test showed no major loss....did a vacuum test showed spot on...so i bought a obd scanner it came up with evap fault p0443 and long term fuel trims -25 and short term trim -20 did a reset of codes and did a drive cycle but fuel trims are returning rich readings again im at a loss please help guys before i jump under a lorry