Generally when you start leaning the LSN you are going to have to lower the idle as leaning the LSN will cause the idle to get higher. It's the opposite if you start to richen the LSN you will need to turn the idle up some. Sounds like when you are leaning the LSN the idle is carrying on and staying high which is making you think it's lean. back the idle back and you will probably be fine as you lean the LSN.