You are asking a big question. There are many, many reasons for this.
Lets hope to hear from those who have lessened it, and how.
I'd say there as many as 50 different causes to this, and some of them iterplay with one another. I hate how jarrs the car, and slows you down. Your car is really broke in well after your record setting trip, so we can eliminate stiff, tight driveline.
I'll put my 2 cents in later.
Skip White