Recently replaced mine w/ the metal WP. No change in temp for me.
The metal WPs that I have seen do not include the housing. Terry Haines (I think) pointed out that if replacing the WP, but not the housing, the stainless steel shroud inside the pump housing needs to be inspected. Sometimes when the pump fails it damages this part, increasing the clearances (sometimes dramatically) and reducing the ability of the WP to pump.
Most of the plastic WP's come with the housing, so this is not a problem.
The SS shroud on mine was undamaged, and the pump works fine.
Richard
