Pontiac Repair: engine running poorly after repairs, vacuum lines, gas mileage

Question
I have Quad 4 Grand Prix LE (1991) which recently had the water pump replaced. Since I got it back, it has lost power and runs very poorly on take off. It seems to smooth out at about 50 mph. The oil is clean and free of water and I don't hear any exhaust escaping around the head. I've found no vacuum lines missing or unattached nor any wiring that seems out of place. I've only owned the car a couple of weeks, but I know it was running much better before this repair. Of course, gas mileage has suffered greatly. Help!

Answer
Hi, this could be in the firing, one of the plug may not firing like it should, most of the time the coil housing will cause this, it also could be that the timing is off just a little, if they remove the timing chain to replace the water pump, they could have got the timing off, when putting the chain back on.