I put my 2 12" infinitys in my friends B3000 pickup with his 900W rockford amp. Its only a single cab. We had to set them on the passenger seat. It only cost us 15 bucks to enter so it wasnt a complete waste. Doesnt 131 sound a little too low??

131 is anything but low, but maybe you sucked all the air in the cab and the speakers started to cavitate?

So you had the box sitting on the passanger seat right, up and down of across the seat? Where did they put the microphone? Floor or glass?

131DB isn't bad, but I think it could be higher for 900watts and in a truck. My 2 10'* and 1000 watts best so far is 138.9 db. but when I started it was 135 ish. What did you use for the song or test track? You might not of hit the right frequency for the vechile, 30 seconds isn't a lot of time to play all kind of test tracks and sweeps.

You guys are going to be deaf by the time you're 40