RT 680.  I got the same question in with Rec Tec.  Seems like I may have to offset the temp but the left right difference is a lot.  All probes were good in the ice bath at 32 deg. 

I used a thermal camera a few months back. The right front definitely has a hot spot at higher temps. After 30-45 minutes at 250 the temp was pretty even across the entire grate.

I calibrated mine with an ambient probe in the middle. The offset ended up being -1%.