Roachie I think they are 85 or 90 pto horse power. Don't hold me to that. If I remember correctly there is a screw on the top back side of the pump that does the fuel but I can't remember if it goes in or out. Sorry maybe this helped a lil bit. lol
Should be a DM4E Stanadyne... Not much you can do without tearing into the pump. The screw that has been mentioned increases fuel when screwed out. But, also as mentioned it won't do much, maybe 5hp, 10 at most. If you want to try something a little more involved there might be one more adjustment that doesn't involve completely disassembling the pump. Not quite sure though, been into the DM4 pumps, but not the DM4E, shouldn't be much different. PM me if you're interested.