So . . . every step in the Tune-up affects the others. They are all equally important. If you leave one out, all bets are off. The "Decent Tune-up" is a compendium of many peoples' efforts over the years and years. It is worth learning and doing. As I recall, it is six basic steps including setting the CO Fuel Trim with guzzidiag, baselining the TPS with a quality voltmeter, adjusting the valves, balancing the throttle bodies , and drinking beer.
I could have one or two of those steps out of order . . .
These are the two most straight-forward starting points to baseline any V11. Cost? About a hundred bucks US ($75 for the cables and about $20 for the relays. Add maybe a hundred bucks for a balancing tool like TwinMax or whatever.
The PC is obsolete. Your throttle body rubber blew because the throttle bodies are out of balance and the rest of the parameters are out of tune.
GEI are under rated and will not suffice. They fail. They are not up to the current demands in more than one location (#5, #2, and possibly #1). This is well established. The fact that under-rated relays contribute to running (and other issues) has been established unequivocally.