Allright here we go.

I am addicted to temp probes. I mainly use 1) Temperature 2) Sound 3) performance (in order of importance) to tune an engine.

I use a $35 infrared probe like the raytek. Most are these are accurate to +-1 degree and for our purpose it doesnt matter really!

Cheap <150 engines.. you wanna run em at around 195 during break in and about 250 for normal running.

High end $300+ engines ebreak in at around 225 and they run anywhere between 275 and 350 easy!
On top of that they last twice as long!
Can you say "Get what you pay for"?!

-ram