I just replaced my motor in my 1996 silverado with a new gm goodwrench engin, and after starting it it idled poorly and white smoke was comming out of the tail pipe, which is prretty close to what the old motor was diong, which points to the intake manifold, but I had that tested, and cleaned and they said it was ok, so 1) Can they really test the intake when they had just the lower half? 2)could the distributer being off slightly cause white smoke since it is computer controled timing? And 3) if not the intake and presumably not the new motor what else could it be?

Wade

P.s. It is giving me a P1345 code and after running for about 45 seconds the passenger side exhaust manifold is much hotter than the driverside, if that means anyting.

The P1345 code is caused from a variance in the cam position sensor to the crank position sensor. Youll need a scaner to adjust the dist to get the two back within spec.
If you baught a "goodwrench" motor, there covered
by a 3-year/50k mile warranty, that covers parts & labor, but not if you incorrectly assembled all the
parts that were transfered or were defective.
Did you use the correct int gaskt & follow the torque sequence? Very low torque/multiple sequance, 71 in lb-106 in lb-11 ft lb, w/plastic gasket w/rubber insert. Check oil level, its not high
is it, internal coolant leak? Pull the plugs, is there one specific cylinder, pair of cylinders or bank that there is a problem with or all of them? Was there an
existing problem with the old assy, what happened to the old motor? Fill the picture in a little more.