Engine Performance problem
1994 Mercury Tracer 4 cyl Front Wheel Drive Manual 220000 miles

Ever since I got the car, the car had a high idle when it was cold. When I started the car on a cold day and the RPM's dropped real low, the engine would sputter and then go up to 2000 RPM until it warmed up. If I did the same thing and tapped the gas right after I started it, the car would go up to 1500 RPM and stay there until the engine warmed up. When I first had high idle problems, the car would idle at 2000 RPM until I pushed the clutch in. Then the car would rev up and go to idle. All of a sudden the engine started idling at 2000 RPM whether it is cold or hot. Every 5-10,000 miles I had to change the spark plugs because they were hot. I checked the engine code and it said air temp sensor. I changed that and that didn't fix it. So my brother told me it was the IAC. That was not it. If I unhooked the IAC the engine would run at 750 RPM after it warmed up. I checked the computer again and it said MAF. At 168,000 miles, the seat fell out of the head and the head had to be machined .003 in., 2 new valves, new seat, and a new piston, and was rehoned. This was due to a vacumn leak. I found a vacumn leak to the e-vap can and I replaced the PCV valve and the rubber boot. Now the engine only goes up to about 3500 RPM and won't go any higher.