Engine light stays on (Not Flashing) and the engine idles roughly varying from 800 - 1500 RPM's.

Just had a battery swap

Changed Coils out myself 6 months ago (Coil #4 did have rust)
Changed Fuel Filter out myself same time
Changed both 02 sensors myself same time

Oil Change and Filter good since light came on, air filter looked fine

Had the Pump and Fan R2'd at 90K to be safe, no issues.

Car now has 112K on it, friend has cable and program and will be hooking up to it next week to take a peak, but until then the car has to be driven unfortunately.

Car typically gets 31 MPG on Highway (All my driving is highway 120 Miles daily) but has dropped down to 26MPG since the idle thing happened.

Plugs? Software?

Am I looking at danger by driving this thing? Book recomends I drive it gently and get it looked at (Unlike the flashing engine light which means pull over immediately and call for a tow).

Any feedback would be great.

Thanks