I'm not sure how you can differentiate these things. If they want to run different radials, good luck to them, that is their choice. Pump fuel? That is not a definite and it is also their choice. And how do you quantify that their tracks are slower? None of these things realistically effect the times run in that different people choose different tyres, fuel and suspension. The main comparisons are there for all to see in so much as everything else is on a fairly level playing field.
Also, I recall a certain GTR from Japan a few years back attended a drag meet a Willowbank and couldnt run any better than its best time of 7.67