As the title says, I use the AI to improve my setups. In the setup guides I found on the lfs manual, it was written that I need to do consistent laps in order to see how a change in the set affects the time. But I can't drive consistent enough, so I put an AI (pro dificulty) with my previous best setup on the track, and another one with the changes I made to it, and compare their times on qualification, 5 lap race, 10 lap race and 1000 lap race (while I sleep). Till now I thought this is the best way to see which set is better, but now I'm hesitating a bit, because, I used LFS Replay Analyser and got the suspension, brakes, gear ratios and tires from the WR replay, put them in my best set, and compared my original best set with the WR modified one, and mine was about half a second faster. I myself drive at about half a second faster then the AI when I'm at my best (most of the time half a second slower ) but I still am 3 seconds slower then the WR.
This can only mean one of these:
-The WR holder is not good at car setups
-I can't drive
-My method of comparing setups sucks

So, what are your opinions on this?

I wouldn't leave any kind of setup analysis in the hands of the AI. They may be fairly consistent (they do improve slightly over time though) but they cannot drive at the limit of the setup (and it's only at the limit of the setup where most setup changes will be apparent). You should work on being a more consistent driver so that you can do the analysis yourself in the future.

The ai are programed to limit tire sliding. WR setups are made to slide. So there is your problem.

This confuses me a little, isnt drifting/sliding supposed to be slower than gripping?

yes and no.
a certain amount of slip will make the car faster.
when making a low speed turn for example, you want the front to stick but the back to slip out just a little. this will help the car rotate and make the turn faster.

the AI drives a set course.
even with the worst set possible, they will not vary the path they drive.
faster sets need different routes

On some tighter corners it can be quicker to side the car in, as it means you are braking later and using tyre scrub to help slow you down.

I sometimes use AI as a support for long races setups preparations (distances of 100km)
when I need to prepare myself a set for a 100km race on a new track after I'm done with the hotlap settings (based on WR and some set from the net) I simply put AI on the track for the full distance just to start adjusting the tires, after AI can do a full stint with no problems then I start to test it and change it myself
it always requires a lot of changes but, as I can run LFS with AIs in the background to do that (usually while I work ), it saves me the time of the first few outings on the race tires, it simply gives me a better starting point to work on the race settings myself
it is by no means an alternative to work on the setup by myself, it's just a way of saving some time in long races setups preparations