[QwertyManiac]

Johnny Storm races are pretty easy and necessary to master the game actually. But its not necessary to complete them, just go on with the story mode, you'll do fine enough with the races and other things to move on without speed upgrades from Johnny.

And that trainer, well it looks like its controller-activated. Don't know if XBOX trainers exist but this one looks like it!

But just don't bother about Johnny Storm races until you complete the game off (You just have to race him once, as your first mission). After game completion you'll have all time to beat him in as many tries you want. And what's more, you can leap 5 buildings across playing Venom.