Pontiac Repair: oil usage, catalitic converter, consumtion

Question
I have a 2002 Grand Prix SE.  It has a 3.1 L V-6.  Approximately 10 months ago the engine had to be replaced.  Something internal broke and caused major issues.  I had a rebuilt engine installed.  Before the engine replacement, I never had to add a drop of oil between changes.  Now, the new engine is requiring approx. 1 quart of oil per 1000-1200 miles.  The engine company suggested replacing the PCV valve, but that fixed nothing.  The car does not smoke at all, and runs great.  I don't think it is burning the oil.  Also, the front right sparkplug is always oil soaked and badly carboned up.  I have to replace it every few months.  The engine company suggests that it is a problem with the intake.  The intake is the origial off the old engine, so their warranty does not cover it.  My question is, why would the same intake now cause this problem.  It started immediately after the change. Could there have been an istallation error or problem?  I am trying to get an idea of what might be causing the problem before I return to the shop that installed the engine for me.  I would appreciate any suggestions that you might have.

Answer
Hey Brian:

Heres the deal.All engines require some time to "break in" but after a few thousand miles the oil consumtion shoul let up. Also all engines do use some oil even know you may not notice it on the dip stick they do use oil!! If you are adding that much oil ever 1000 miles that is way to high. I assume it's not leaking it on the ground?? You will not see it burning oil due to the catalitic converter reburns the oil vapor. If that plug keeps fouling out the issue is in the cylinder. Was this a new engine or a rebuild engine put in the car? Was it a"long block" engine complete with the heads or a "short" block just the engine minus the heads? I know you said you reused the old intake. The pcv valve is not the issue here but make sure it is the correct one for the car and not a "fits all" unverval one. If that were the case all of the cylinders would sho some signs of oil on the plugs and mainly the 2 rear one #5 and #6 because the pcv feeds theme first. Now back to the intake. No the manifold is not the issue. the gasket however could be If it's not seated correctly agains the heads in could be sucking "air" crank case vapors in to that cylinder. A quick check is to do this pull out the pcv valve and also the breather tube to the air inatke hose and cover both of them up with a piece of plastic or something that will not let air to sneak in. Then get a can of carb cleaner and spray it into the hole in the front valve cover where the pcv valve goes into if the engine picks up speed or start to stumble then that intake gasket is the culpit. Not really likely because the engine would run erratic all the time and more than likely would turn on the ses light. I have seen High milage cars the gasket go bad and cause this to happen but not in 10 months go bad. Okay enough on that back to the engine it's self. If you used the old heads You could have a bad valve guide or seal cauing the oil consumtion. If you got a long block it could also be the same thing a bad guide or seal or maybe they forgot to put a seal on the intake valve?? Things like that have happend. last cause could be a bad cylinder leaking issue. the rings may be bad or something to that affect causing the oil consumtion that could be found doing a cylinder leak down test. That is all of the possibilities that I have for you sorry It's not an easy fix and I'm sure your getting the run around and hopefully I can shed some light on the subject. Good luck :)