Mitsubishi Repair: Driving hesitation or sputtering, 2000 mitsubishi galant, mitsubishi galant

Question
2000 Mitsubishi Galant ES, V4. O.K. A little history first. Stupid I know, however; timing belt broke while driving and had it fixed.  Evidently I was very lucky.  No damage to the top end.  Compresion tests are good.  Although since then and posibly related to it or from towing the car: Replaced broken manifold on top of engine (cracked where it goes into the engine housing), replaced motor mounts(which eliminated major vibration noise that occured after break of T belt), replaced brakes and tires as well.  Ok. major problem, since the new timing belt install, is a sputtering or hesitation at high speed when foot is taken of accelorater.Usually between 60 and 70 mph only.  It's a drastic feeling of jolting or even pull back.  Everything is fine when there's constant pressure on gass peddle. Trans has always performed fine and I don't know why a new T belt would effect trans.  If you could offer any advice, I would be truly greatful.  Thank you for your time.  

Answer
Jim,
It's possible the timing belt is off a notch, or the if the balance belt was also replaced along with the timing belt, it may have been installed slightly out of phase.  This can cause the problems you're describing at higher speeds.  If the tensioner or idler pulley was not replaced at the same time as the T-belt, these may have failed as well.  Find out from the itemized list you got from your mechanic if the balance belt, tensioner, and idler pulley were all replaced at the time your T-belt was replaced.

If it was the intake manifold that was replaced, this could cause sputtering if the gasket was not properly seated.  All intake components should be inspected as well.  The intake manifold is a pretty durable piece, and it would take some serious pressure and heat to damage it.  The severe environment that caused your manifold to crack may have also caused problems with related intake components.

You should also have your fuel pump and fuel injectors inspected to be sure they are performing as they should.  It would be a good idea to replace your fuel filter if you haven't done so within the past 3 years.
Good luck!