Engine Performance problem
1995 Mitsubishi Mirage 4 cyl Front Wheel Drive Automatic 110000 miles

I have a 1995 Mitsubishi Mirage s 1.5 liter and I just did a tune up and replaced all the belts. When I start it up it runs good shakes a little in park or neutral but when in drive or reverse it idles very badly and very low as if it wants to cut off until I hit the gas and then it runs good. The car had been sitting for over a year and I did replace the air filter also, could it be the fuel system or timing please help!