the high idle is normal when cold, i've seen mine idle as high as 2300, but those are on the coldest of days(-50 or colder). the rough idle might be caused from the exhaust leak. im not sure what the deal is with the drop in idle when the engine is free to idle, but mine does it too, but it bounces right back to 750. i think its my intake or something, either way, it shouldn't hurt anything