Volvo Repair: 94 850 wagon, oxygen sensor, normal 1

Question
I just had the clutch and timing belt changed. The car ran great before the repair but after the mechanic said the coil went bad so it was replaced. The car still had no power and ran very rough but the check engine light did not come on. He then replaced the idle control motor but that didn't help either he then said it was the oxygen sensor but i said no and took the car home. Also now the tach drops to zero intermittently. It seems to get worst the longer the car runs. On the B terminal I get normal 1-1-1 codes at 2 & 6. Any suggestions?  

Answer
A 2 IS IGNITION AND FUEL.IF IT RAN WELL BEFORE IT COULD BE A WRONG INSTALLED TIMING BELT OR FLYWHEEL.MOST THINGS THAT RAN WELL BEFORE BEING WORKED ON AND DON'T AFTER ARE USUALLY HUMAN ERROR.NOT ALWAYS.I WOULD TAKE IT BACK AND TELL THEM IT WAS FINE BEFORE THEY TOUCHED IT IF THEY DO NOTHIN GGO TO SOMEONE ELSE TO GET A DIAGNOSIS AND IF THEY DID SOMETHING WRONG YOU WILL NEED TO GET THEM TO PAY FOR THE REPAIR OR TAKE THEM TO COURT.