Ignition Fusible Link Blowing after Lean Burn Conversion

You need some protection so you can troubleshoot it. One thing I have around here is an old stop/ tail socket, with 1157. You can wire this several ways for testing. Wire both pigtails together, and use that point for one terminal, and the shell for the other. Put that in series with the battery ground for testing. Now you have protection, as the bulb will keep anything from burning up

You also might consider buying a couple of those universal /automotive circuit breakers, maybe a 15 and a 20A. Do the same with them. Now instead of burning up wiring or links, the breaker should sit there and cycle.

Start disconnecting stuff systematically, and I WOULD START with whatever you modified, as that is the likliest source. Next would be the VR, unplug it.