When toyotoa engines start getting a few thousand miles on them, they actually start breaking in so if by what you mean "less throttle delay" means faster acceleration, then its just the engine breaking in and putting out all the power it has. As you add more miles to a a japanese engine, it starts breaking in and performing better and thats a good thing. Thats why this engine will go 400,000+ miles with no problems. I;d say by the time you get to 10,000 miles, the engine will be fully broken in and at full power. Pz out.