So my 98 frontier 5 speed 4x4 with the ka24de has been having some problems lately. I was getting 250 miles out of a full tank now I only get about 180. Upon startup when the engine is cold, or if it's in gear it idles really high. When I take it out of gear, and only if I'm stopped it will idle normally. Replaced the tps after it threw a code for it. Not sure what it could be. Ecu maybe?