Not sure if you have tried this or not, but try running without hood and see the difference in temp you get with just that. I fought overheading this summer also when temps were over 100*. I ended up getting a be cool radiaotr that helped alot but that left me no room for a puller type fan. Switched to a single 16" fan and installed trans cooler on rest of radiator and wired that fan also into temp control. Here is electric fan I am running:
http://www.summitracing.com/parts/HFM-ZFB16S/
Now back to why I asked about hood. After all that I still would over heat on highway or fast then 40 mph cruising. I could run it in garage all day and at track and never over heat. But, if I ran with out hood it would stat at 190* or below. So I ended up taping of the scope and would never get above 200* even when it was over 105* or so outside.
Sorry for long post but just give it a try without hood and should tell you if that could be causing your problem. I see you have a plate but could not tell if it actually sealed to hood or not.
Troy