I have a 1994 GMC S-15 Jimmy and I just got done redoing the valvues, heads, etc. Everything runs great now on that end, but there is a problem that has got me stumped. After the vehicle is driven for a few minutes and you come to a stop sometimes there will be white smoke coming out of the exaust pipe. It doesn't do this all of the time and all of the fluid levels are fine when I check them. There are no leaks that I have found, so any suggestions would be appreciated.