Mopar has fallen off the TC4 bandwagon for his racing, so take his advice accordingly.
There is no need for expensive upgrades to race a TC4 in VTA. I actually "downgraded" from a spool to a plastic diff in the front of my car. The diff is easier on the front cvds and lighter. I was able to run the composite bones without any issues. (Note: I did have to adjust my setup to work better with a diff)
The only reason to upgrade the stock plastic shocks is that threaded shocks are quicker to make small adjustments to ride height. The stock plastic shocks work well if built properly.
The only "upgrade" needed on a TC4 is a wider bumper, which will help protect the steering rack.
I currently race a TC4 in VTA and I have been able to be competitive with it locally and nationally. While there may be "better" cars out there, the TC4 has been a great value for me.