Any ideas ? pinging

I just got my car dyno'd - was running great. Good A/F.
Maybe 2wks later it has started pinging. very noticeable at low rpm part throttle.
The only thing that changed since then was the air charge temp sensor.
I cleaned the MAF.
mods
K&N - C&L - 70MM TBI, TFS intake, 2030 Crane, headers, Superchip, GT40p's
I am going to a buddies to use his timing light and vaccuum gauge to check the obvious but was hoping for other ideas.