06 Jetta TDI. Car has been nothing but problems since I bought it. Replaced cam and lifters about 30-40k miles ago. Probably a few month or so back I started getting some black smoke on start up. Not enough for me to see but a friend said so. The past few weeks its been worse, after idling at a stop light or even a stop sign. Hesistates like it doesn't want to go past 2.5k rpm while blowing black smoke. I let off the accelerator and then give it gas and it'll go forward. Just recently past couple days its billowing white smoke. Did an oil change a couple days ago. Possible correlation. Still blows black smoke and hesitates occasionally.
Where should I start?