Help with rotary axis please

Hi all
I run a home built CNC router with a rotary axis attachment. The thing works fine except that I cannot get the rotary axis to rotate as fast as I would like (and I'm sure it could). The router has 2 steppers on the x axis so I cannot use stepper wizard to configure it.  I am hoping that someone could take a look at the attached .ini and .hal files and tell me how to improve things.
Thanks for reading, and thanks for any answers
Aaron

Thanks for your reply.  However as soon as I make max velocity greater than 500, and I jog the axis it will speed up then slow down to run at a constant speed, then when I stop jogging it will speed up again then slow down to a stop.  Very strange. Then If I run  job with max vel. greater than 500 I generally get a joint following error.
Thanks again

Yes. This is a parallel port machine.
I have to admit I don't understand this stuff too well, but the latency number I used is 25093. 
If I reduced microsteps from 16 to 8 would that help, or would it have undesirable effects?.
Thanks for you time.

I have changed the settings on the stepper driver from 16 to 8 and It seems a little better,.Als tweaked the .ini file to this;
MAX_VELOCITY = 1000
MAX_ACCELERATION = 3000
MIN_LIMIT = -999999999.0
MAX_LIMIT = 999999999.0

[JOINT_4]
TYPE = ANGULAR
HOME = 0.0
MAX_VELOCITY = 1000
MAX_ACCELERATION = 3000
STEPGEN_MAXACCEL = 2500.0

But am not sure what to do with stepgen-maxaccel.
Thanks again
 

Thanks again for replying. 
Stupid question, but what do you mean by 25* bigger than the associated MAX.  Should it just be bigger than 3000, like say 3500?