Since people are speedrunning archives now.
Mercedes-AMG gt3 (Victory by design):
Minimum strategy has changed. It is discovered that 3321312 is enough to complete (1 less gold upgrade for body than previously listed).
Newer strategy costs 151 gold and ~760k R$ (60 less gold)
With the ongoing sale, 105 gold and ~530k r$
Mazda Furai (Furai Rising):
Minimum strategy has also changed, by quite a bit. 1132123 is enough to complete the event (2 different gold ups instead of 3), although it is rather difficult.
New strategy costs 105 gold and just over 1mil R$ (65 less gold)
Ferrari FXXK (No Compromise):
This has been noted on the strategy page for a bit, but I'll post just in case. It's possible to complete will al-r$ upgrades and spend 40 gold to skip 8.3 speed snap. Original strategy included one gold upgrade on top of that.
Lamborghini Huracan Performate (the Perfect Storm)
1131111 works too, for 30 gold.
Old strat is 1311111, for 38 gold. These two give the same speed/acc boost but costs different.
@Jean M.S. discovered this. It probably applies to absolutely nobody.
FERRARI TESTAROSSA (Road Trip):
I don't know why the minimum strategy is more expensive than the one that gets you to recommended PR.
Porsche 911 GT2 RS (King of the Ring):
I've discovered that 1331313 might be a potential option (saving over 100 gold from the original 1333333 and over 60 from the now-listed 1333313). However, this has not been verified yet. Once it is, the page will be updated