The new seasonal event, Supercar Festival, is quick money.
I'm running the Mazda Furai Concept @ 550pp, turning in first place finishes with 14 seconds to spare, clearing 1.23 million credits on the Fuji event - and I'm at 110% payout!
I tried tuning it down to 520pp (100 less than max allowed), and still took 4th place, 10 seconds behind 1st, and cleared 683k credits for that run.
I'm working my way down to see how low I can go and still win - 540 or 534 should be totally possible, and well over 2 million credits @ 200% payout, I'm thinking.
ETA: @ 130% payout and 540pp, Furai just netted me 1,444,050CR on Fuji event (Performance Difference Adjustment of 1,026,880CR).
While not an *easy* win, it was a win, by 2.45 seconds, and that included a spin on my part.
Oh, and 143,550 XP as well.
ETA: 535pp, 3.458 sec win, payout (130%) 1,508,230CR, 149,930XP.