I was in a 190A8 last night, and pulled up my clipboard... I noticed the E6B listd 1.58 as the max boost on WEP, but the actual instrument read 1.63. I turned WEP off and checked that also. E6B said should be 1.32 boost on milpower, but it was pegged perfectly at 1.3 even.
I was passing 10k on auto climb at the time. Took a screenshot, if it's needed.
I think the instrument dial may be mis-calibrated.