fuel pressure riser? sounds like your talking about FMU. fuel management unit that runs off a ratio (ie 12:1).

basically thats the WORST type of fuel management you can use. it'd really be worth it to get dyno tuned with uberdata, or if you have a ton of money, hondata.

a narrow band a/f gauge wont be able to tell you much.

im not sure about adjusting the internal. my internal is the non-adjustable. sorry i can't help there