Problems with bass cutting out and good box specs

[nucleus]

Hey guys this is a pain in the ass. When I turn it up the subs stop kicking.

Ok 1st off I run an Alpine mrp-m500 Mono Black amp to power the 2X Rockford Fosqate Punch P2D212 12ich subs. This is wired up in the 2 Ohm config as per the Rockford Manual specs

The Whole system runs though the Ford Factory ICC to keep the steering controls. The factory sub has been removed and a line convertor has been put in its place to convert the signal from the facory amp back into RCA for the alpine amp with the gain adjustments on the line.

I have everything right down on the amp so as I turn the gain on the amp to the normal half way mark it cuts out again ....... What is wong, please help?

(P.S. I tested it in a mates car with similar stuff and it works much better......)

Also if anyone has ideas for box specs to put the 2 rockford subs in let me know.

[Poelwyk]

the car runs a 4 Gauge Wire to the amp and a 4 gauge to the body of the car aswell the box that the subs are in atm is just a Automax box ....aswell