2001 Mitsubishi Galant idle speed after timing belt replace

I recently had my timing belt replaced. When I got the car back, it was idling roughly. I brought it back and my mechanic raised the idle speed- so the vibration would be less noticeable! It now idles at 1100rpm in neutral and 950 in drive. When I am slowing down and the engine hits 1000rpm you can feel the vibration in the steering wheel. It is also noticeable when accelerating up through 1000rpm. I think the engine is slightly rougher throughout the rpm range, but it drives well and pulls strongly through the rpm range. I still think something is wrong- before I had the belt changed, the idle was smooth- at 750-800 rpm- with no roughness at any rpm. I brought it back a second time and my mechanic said 2 wires (between the coils on the valve covers) were arcing- he changed them. The problem still persists. Help?