904 slow 2-3 shift, should I be worried?

I totally agree about the adjustment. What's happening is a common problem in these transmissions. The slow 2-3 shift is actually the transmission trying to engage 2 and 3 at the same time. A lot of times it's because the 2nd gear band is adjusted too tightly and is still a little applied on the 2-3 shift. The TF2 kit has a corrective orifice that you knock in one of the passages in the transmission that slows the fluid flow and allows the 2nd gear band time to release fully. Usually adjusting the band a little on the loose side will cure it. Usually.