Things you did/upgraded that surprised you how helpful they were

I just noticed this was in the race form so I'm taking it now in a raceway my first post on the subject I was just looking at recent posts and didn't notice what section it was in...
As far as when I was drag racing more regular which wasn't very regular the slicks or street drag radials was the number one. Number two was more carburetors LOL...
And finally not listening to all the internet gurus and just trying different small things...