Can anyone shed some light

I know this is an old issue but cant seem to find any conclusive answer anywhere. Im a newbie and never had these issues (besides PAIR) with my Hayabusa.
I have bought a 2009 model (CAL version) with std headers. Bike came with two locally manufactured slip ons fitted. I removed the CAT from the header. Sounds great however runs a slight bit rich on top end (dyno tested). I want to look at converting the std headers into 4-1. I dont have a power comander and dont really want to put one in at the moment. They are pretty expensive here in SA. Air Filter is a DNA filter. Oil is Castrol Power Racing synthetic.
The bike is used for general riding and not drag racing however the occasional street race.
Questions
1. Has anyone done this and how has it affected the bike (performance, decel pop, power etc)
2. Can you explain/send pictures on how to do it. What to look out for? Must I convert 4-2-1 or can I block off left outlet?
3. Must I do the "marble thing" on the PAIR?
4. What can be done about the richness without fitting a PC.
any help would be great

G,day untamed I gutted my cat outta my 2010 ZX1400's header and had a plug made just to block off one side, I did this to go the 4-1 but my MOF bitched about how the ZX14 would look odd & not look balanced lol so I didn't end up using it! but using my Idea you could always go back the other way if ya dont like it or ????

Thanks very much Bean07 for the idea of the plug. My worry is that I lose a bit of midrange power by just blocking it off. If it turns out Im right then as you say I can go back to the current set up. I get 178HP on as it is but think it looks better with one pipe, and hoping I gain a few more horses.