Need help.  This is a 1978 Hawaiian jet boat.  I do not know what the hanging push pull switch is?  There are 4 on the dash.  one is the lights, one is the bilge and one is the blower.  The one hanging has only 2 wires going to it.  One wire goes to ignition switch and the other wire runs to the back into the fuse panel and it is labeled alternator.  Which is has another wire connecting over to the next pin which is labeled battery.  Whether this switch is pushed in or pulled out seems to have no bearing on anything.    I am trying to find parts (the pull knob and hardware to secure it to dash) so I can actually have it in the dash instead of just hanging underneath.  Really just wanting to know what it is for?

I am needing help on tuning my engine I just had rebuilt and some changes where made to it.   Anyway here is what I have and where I am currently at.  I will be looking for advice on setting the base tuning to get me out on the water.  To note I also want to tune it conservatively as I can not use all the power anyway.   So here is what I have:
Chevy 468 LS6
8 to 1 D dished pistons
Engle TCS-7 HYD cam
Race Aero twin turbo system with intercooler using Rayjays
Single Holley blow thru 850 double pumper
MSD 6AL
MSD BTM 8762
Holley Red electric fuel pump - had a mechanical but last shop pulled it off.  Worried that the Holley Red will not provide enough psi under boost and should get the mechanical back and put it on.  Seemed to work fine before.  Think it was just the mechanic's preference.
fuel regulator

I would like to note that this was a proven system for almost 20 years and ran great.  The changes to the system are now the fuel pump and that it is in a 28ft Hawaiian jet boat.  Came out of a 28ft Fountain with outdrive.  The jet has a stage 2 and is rated for 600hp.  This engine was close to 900hp.

I currently got it to run on the trailer and all seems okay.  But I want to tune it now.  So I have the advance at 3500 rpms at 32 degrees and at idle it is around 18 degrees.  Gap on the plugs I believe is to wide at .050 and think I should narrow them to .025.  When setting the idle it seems to like 1200 rpms and anything lower then 1100 starts to get a little jumpy.  When turning in the 4 mixture screws doesn't change anything so I backed them each out 1 1/2 turns.  This being the first time for me and not that knowledgeable but learning as I go. 

My goal is now to just to be able to use the boat.  I want to keep it conservative and will not be racing it.  I am also not really sure what to set the BTM at.  I will always just use pump 91 gas.  So not sure if I have to turn the dial up to 3 or set it at 0 or what?

For tuning I would also like advice on steps of how to do it meaning what do I set first, the idle mixture and rpms or the carb or the idle timing?  It seems okay and I was able to run it for a little bit on the trailer parked in the lake.  Was a little rough pushing the throttle up to 3500 rpms as I did it slowly.  Not sure if that is from too wide a gap on the spark plugs or the fuel pump, but I think it should be smoother then what it is.   Also if I rev it quick and drop it back to idle it dies.

As I said before I am worried now about running to lean with this fuel pump and destroying my engine now.  So I am afraid to take it out until I make corrections to what I have. 

Thank you for any help on this.  I am really close this time and am so excited to being finally able to use the boat.