Load axis question - alpha n or MAP

I'm a little bit lost as to what i should use for my load axis. I'm using a link g4+ on a turbo RB30 with quite a large cam. The tune i had done a while ago now is still in the ecu, and used tradiational fuel equation with load= bap/map. It was tuned for E85 only and now i would like to tune it myself for pump fuel as E85 is not available in my part of australia, and im sick of buying it by the drum. i would then like to tune for flex fuel afterwards, hence the re-tune. I would like to use the moddled fuel eqaution/multi fuel. When the car is running the vacuum at idle is 4"hg, can this work at all with MAP for load or does it have to be TPS for load - because trying to tune a turbo car TPS based as someone who is very new to all this scares me. I was also wondering, if it cant be done, what is the rule of thumb for too little vacuum at idle to use MAP. Thanks!

In this case since you have a fairly weak vacuum signal so it is not going to be a good indicator of engine load. I would do it similar to how we typically set up a RB26 (itb's). Set load source to MAP. Use TP on the y axis of the fuel table. Make sure open loop lambda target table is turned on and set its Y axis to MAP or MGP. Initially tune the main fuel table on lowest wastegate boost. Once that table is tuned, bump up the boost and do a power run, it it drifts rich (or lean) at higher boost levels then you need to turn on a 4D fuel table and set that up with MAP or MGP on its axis and use that to adjust the fuel for higher boost levels. Typically that 4D table will only need numbers in a few cells at the bottom right corner, most of it will remain as zeros.

I think there is a couple of webinars on this tuning method.

Here's one: https://www.hpacademy.com/previous-webinars/163-tps-map-tuning-for-turbo-and-itb-alpha-n/