1990 K1500 350TBI 5speed manual

I am completely stumped. My gauge shows my engine never makes it past 140F. I have taken several raytech thermal guns and have checked the temp. The hottest i have ever seen it get was 150 or so.

I replaced the tstat with a new 195f and replaced the coolent.

The heat in the truck is warm, but by no means is it hot. I have checked all the hoses for possible issues and have not seen any.

also replced the temp sensor.

On another note has anyone else experianced a front end whistle at around 35 or so