I’ve heard of t9500 CPUs working in the 2007 but not the t9550 I know a macbook has this processor and the tdp is the same as a t9550 so I think it will work but I need imput
I have never heard anyone trying this chip in a 20” iMac. The best you can install is what Apple had used in the series. Here’s a listing on the possible CPU’s iMac7,1