X5 4.4 2001, Cold, Whitesmoke, Misfire, help!

[turquise1]

Hey ppl,

I have an X5 4.4 2001 with 160k miles. Recently after an oil change, another day in the morning, I experienced a misfire at cold start and big amounts of white smoke coming out of the tailpipes.

There was no leak, first I thought it would be just humidity doing this. I blamed the Oil Separator and I changed it and its two major hoses. After white smoke cleared, we drove the car for another couple of weeks before it got really cold again recently. Again in the morning a misfire (blinking engine warning, checked with a computer) and in 15 mins, a huge white smoke. I havent seen any leaks around the car, also checked the dipstick and the oil looks clean (no milky look). The coolent needed some filling up though, which led me to believe there would be a gasket leak (hopefully not!) somewhere.

What would you recommend? Are those block leak testers reliable to see if there is a leak?

Thanks for all the help in advance..