From Rockford's web site, the Punch 401SP was sold at Authorized Dealer "Audio Express" with minor cosmetic changes to Punch 401S. Checking the manuals for both (model year 2003) they are the same amp. I would go with the parts listed on the schematic Perry posted.
They are the same amp. Audio express had the board color changed by Rockford, added the maximum watt rating added to the badge with a little fake carbon fiber in the emblem. They wanted their own line if you will to attract buyers and sell amps. I guess they figured if their amps were pro models they would sell more amplifiers.
I see people list these all the time on ebay calling them pro models with way higher power ratings and being listed as rare. They are neither. Same exact amp as the normal model with a blue board.
Pins 1 and 2 would be the same as they were with the other IC if there was no rail voltage. The 2.3v on both pins will cause the duty cycle to roll back. Reduce your 12v supply voltage and the pulse width will increase.