OK... So I fancy myself as an advanced DIY plumber... I have a shower valve (PROFLOW) that sat for a few years without use. There was low/no hot side pressure. Bought a replacement ProFlo PF141558PK Ceramic Single Lever Cartridge With Pressure Balancer For Tub And Shower Valves from a local plumbing supply ($$$) (and supply lines are plumbed correctly). Installed easily but resultant HOT and COLD are now on the wrong sides when turned on. What did I do wrong (other than not calling a real plumber)? Also, what is the second piece shown in the repair kit? I did not see how it was used in my valve.