I'm trying to tune my mtb's 9 speed rear derailleur, but I'm having some problems.

The chain will get to all of the gears, but it is not tightening or loosening quick enough. When I shift up, for example, from 1, it will not change on the first click. then it will shift up lagging one behind, until it gets to the 3rd gear from the top, at which point it will jump the 2nd last gear and go straight to the last.

As well, sometimes it will shift properly, right up until the last gear, where i will have to mash on the pedals before it changes.

I cleaned and re-lubed the gears, but this yielded no change, nor has changing the front ring.

Can anyone give me any tuning tips? I'm using a Shimano XT from last year, so there should be no problem in regards to the quality of the derailleur.