why the heck is the fj1100 headlight so dim?

[mtc]

You really should consider the headlight relay mod sooner rather than later.
You are suffering from voltage drop, just the nature of a 30 year old harness/switches/connectors.
This voltage drop will not go away with a fancy new bulb.

Here is a company called Eastern Beaver who has done all the work for you on your relay mod. Plug and play.
Scroll down you want the H4 with the fairing mounted relays.
https://www.easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html

Eastern Beaver makes quality products. Takes a little more time shipping from Japan, but worth it.

with just the led light , it is much much better and perfectly adequate, and even the blue highbeam bulb burns brighter, that lamp must be 40 years old , everything else tail light, turn signals brake light burns real bright, i can see it being better, buyt for now i am good and staying on course with my budgeting