In my opinion the Aluminium Ball Bearing Steering set did nothing to reduce the slop. I suggest that you replace the Ball cups regularly.
As fas as other options go I would definately recommend the Lightweight Delrin Outdrives for your TA04R. They replace the steel outdrives which weigh a tonn. This reduces the rotating mass considerably and will get you up to speed faster.
Also Work on weight reduction as much as you can. Read the TA04R thread for some of the posts on weights of various parts. Pizza Dude and I have weighed most parts on the car including hop ups with some interesting results.
My brother and I both have the 2002 TA04R Kit. His car is almost box standard where as I have done a lot to reduce the weight and free up the drive train etc. With the same motors fitted my car is significantly faster all around the track. I even went as far as not using the nice aluminium spur gear adapter, instead opting for the standard plastic one. This was to help compensate for the twin aluminium centre pulleys that I used on the lay shaft instead of the plastic ones. This was just for durability over the standard plastic ones.
Check out the TA04 thread for stacks of helpful info.