Mitsubishi Repair: weird problems after timing belt changed, obd scanner, valve cover gasket

Question
Hi,i own a 2000 galant 2.4 .while driving the car gradually lost power.i was not home during the unfortunate event but it was taken to the shop.after getting a call about the car dieing i came to the conclusion that the plugs fouled out due to a bad valve cover gasket.(never got to fixing it before i left) because the car would turn over and try to start.well it went too the shop and they said the timing belt broke.i dont understand how the car was able to start if the timing belt really  "broke" like they say.they said the ignition coils were bad too.so they did the valve cover gaskets plugs/ plug wires/plugs timing belt. now my car has stalls out on me when coming to a stop every now and then and sometimes at idle it tries to stall out then catches  it self and goes up in idle.i have almost no power after 3 thousand rpm and at threee thousand rpm it kinda sticks there. the car drives fine under 3k.it almost feels as if it missfires also but its not bad enough that anything shows on the obd scanner.also anything past 55 the car never goes in overdrive the cruise sets and the rpms stay at 2500.and im now only getting 160 miles to a whole tank.vs my regular 280+ WHATS GOING ON !!!

Answer
Anthony,
I would guess the timing belt is not set properly.  The car may still start, but it would run poorly.  With improper timing, the ECU will retard the ignition timing to prevent engine damage, and that can cause stalling, poor idle, poor acceleration, and reduction of top speed.  If your particular engine also has a balance belt (sometimes called a timing belt B), that could have been installed out of phase, which cause improper engine balance and again cause the ECU to retard the ignition timing.  You may want to have a different mechanic inspect the timing and the belts.  You even may want to have the dealership inspect it as well.
Good luck!