Been meaning to post about this for a while now, but I figured out that if you so much as pull up the tune sheet in GE, it doesn't matter if you do anything in it or not, it gives you all the tires in the game. Like I said though if you do this before buying dirt and snow tires for your car, you will not be able to race it on dirt or snow despite it saying you have them. So yea, avoid touching it at all costs if you haven't already installed them. I am going to edit the OP to mention this.
Also, here are some things I am adding to the FAQ's that I feel need to be pointed out:
What happens if I click the tune sheet on GE 1.3.1. and why do you say not to click it?
Answer: It does the same thing the "Enable All Tires" function on Luca's editor does. It gives you all the tires in the game, even the unused ones, and even says you have the dirt or snow tires purchased already, but no matter what, it will NOT let you race on dirt or snow, even if your car originally supported them. If you want to use the tune sheet, make sure you install dirt and snow tires BEFORE using it.
So I accidentally clicked "Tune Sheet" in GE 1.3.1., what do I do?
Answer: Pretty much, start over. Go back to your PS3 and copy your save from your console to your USB device. Then pick up where you left off, but this time, avoid opening the tune sheet. Again, If you want to use the tune sheet, make sure you install dirt and snow tires BEFORE using it.
I installed dirt and snow tires on my go-kart, but it's still not letting me race it on dirt or snow when I go to practice in GT Mode. Why is it doing this and how can I race it on dirt or snow?
Answer: Simply put, the game has a limitation that prevents you from racing karts on tracks with weather change that for some reason extends to dirt and snow tracks in practice mode. Oddly it only seems to apply to dirt and snow tracks in practice mode and not the rest of the game. If you want to race your kart on dirt or snow, just take it to arcade mode and granted you followed the tutorial properly, you should have no problems there.
I followed this tutorial and my car looks like a standard car now and it won't let me into Photo Travel anymore. Why is this happening and how can I fix it?
Answer: You put a body to a standard version of the car on it. Some cars in GT5 have standard versions of cars that are already available in premium in the game, like the Enzo Ferrari, and GE 1.3.1. unfortunately doesn't have the premium body codes for some of them.
To fix this, you simply need to get the body code to the premium version of the car, which can be done simply by buying it or adding it to your garage via GE, and then copy the premium body code to the car.