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???

LEFT BANK

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!