Mitsubishi Eclipse misses and revs high

Hello all,

A few weeks ago my '03 Mitsubishi Eclipse missed for the first time since I’ve had it. It’s a 4-banger, so it was definitely noticeable. Fast forward a couple weeks and after a trip to Texas (from Tennessee), it begins to run between 2,000 and 3,000 RPM on start-up. There is a lack of power (not attributed to the small engine size) that was not present until a short time ago. It stopped doing that, and today a service engine light came on. The code was P0134. Some things about the car- the oil is changed religiously every 3-4 thousand miles, and the only major repairs were several years ago- the clutch and head gasket. Spark plugs are 2 years old, and coil packs were checked out around then as well.

Any help would be much appreciated.