I usually fly in Maine (on the coat) so field elevation is about 100ft. I'm on vacation now in easter Colorado and flying out here (about 4100ft). I've noticed the plane seems a little sluggish here in Colorado (it flys GREAT in Maine), and the engine runs rougher (want's to sputter and quit more at idle). I do have the needle valve set for this altitude. I'm not worried about running the engine at a higher idle because I have steady 5 - 8 knot headwind all the time, so the plane is not too fast at touchdown (if anything I need more power). I'm flying a Sig LT-40 with a O.S. LA .40 using a 10x6 prop.

Just wondering if anyone else is familiar with this, and any recommendations to improve the engine performance.