Plenum spacer, some hi flow cats and then a Remap but as discussed to a few in the same situation.........unless you go FI your really only picking bits and pieces of power up.
The above is probably costing you the thick end of a grand and your only realistically looking at what 20-30bhp max? Or am I off the mark a bit (can't remember as I usually don't offer any advice so avoid the 'how to I get more power' threads )