Weak AM reception in aftermarket HU

[driving90]

I just swapped out the stock OEM toyota head unit for a Kenwood kdc mp235 a few days ago. overall, i'm satisfied with the unit...FM, CD, and aux in all work great. However, when I flipped to AM, the unit picked up only a handful of stations and they were full of static. everything in my wiring harness job seems to be right and the antenna appears to be working --otherwise i wont be getting FM stations, right?

any suggestions on what i should check? or do you think I got a badly designed head unit?

P.S. on the wiring harness, orange (illumination), and blue (power antenna) weren't spliced with into the aftermarket unit because there wasn't an equivalent on the HU. On the aftermarket HU, the power control (blue, white striped) wire and the brown telephone mute wire was not connected to anything and the "ANT CONT" blue wire wasn't used according to the manual.