You would need to check it with the engine under a load. It will still cool to fast before you could pop the hood after it has returned to an idle to be accurate. The best way will be as Ron mentioned, using an engine dyno or even a chassis dyno, will yield the best results. You also could modify your manifolds or headers to accept thermocouples, and get a multimeter that can read the results. I got mine from Snap-on, Mac tools even has one. Its an EM710, and has a bar graph function as well,and comes with its own thermocoupler lead. It can even be used to diagnose oxygen sensors and fuel injectors and set TPS voltage on fuel injection equipped cars. You probably can only do one exhaust port at a time, but its a start. You can put it on the dash or hold it in your hand as you drive in different terrains and see the effects in real time. Or you could take your hood off and have a friend ride in the engine compartment and use the BBQ hand held infrared checker(LOL) :D,just don't let any cops see you!
