I put a temp probe on the inlet and outlet of the radiator and ran the engine up to about 3000. I held it there for a good minute or two and the temp kept rising. There was a temp difference of 20* at idle with the engine temp at 160*, but at high temp the TD went down to 3*-5* at high rpm.

There is two possible things going on here, either the water is flowing Through the radiator so fast it cant dissipate the heat, or the radiator just isn't big enough.