Exhaust Header temperature discrepancy?
 

I'm back with a new question. I've noticed that a couple of the header pipes have discolored slightly differently over the years. To get an accurate temperature reading I painted a 'dot' on each pipe to give me a uniform 0.98 emissivity reference point. (If you're not familiar with Infrared Thermography and Emissivity Google it. You might find it interesting.)
Here's what I found:
CYL TEMP
1 534
3 525
5 377
7 536

2 567
4 314
6 527
8 509

What would cause #5 & & #4 to run so much cooler? BTW, the readings coincide with the discoloration of the powder coating so apparently it's been like this since the original build in 2011.
Thoughts anyone???
https://cimg0.ibsrv.net/gimg/moparfo...3e890b4781.jpg
LEFT BANK
https://cimg3.ibsrv.net/gimg/moparfo...3193488e88.jpg
RIGHT BANK

I'd check the plugs and wires again but what intake manifold do you have? I have seen the intake cause lean cylinders.

Thanx, Iowan. I think you're right about the intake manifold. It's a stock cast iron manifold and considering - from the minimal discoloration of the powder coating - that it's been that way since day one, that's the only common denominator. As soon as the Powerball people pick the right numbers I'll upgrade it. :-)
In the meantime I'm going to try increasing or decreasing the gap on those plugs and see if it comes up at all.
Thanx again!