It is amazing the difference in IAT's in different setups. I have the same setup and see the same IAT results as the op and I'm also trying to decide if I should do anything.
2011 SS IOM Vert. ECS Vortech 13+ psi, Water/Meth, 2800 stall, LT headers, Drag radials, Drag alignment, Cradle Bushings. Tuned by Ted.