Still not sure why you think the PI is the end-all deciding factor whether two cars will be perfect equals on a track.
That is because you are infering something that was not implied nor intended. The fact is the PI is a problem in Forza 3. It was a problem in Forza 2 and it has became a bigger problem in Forza 3.
You will never get 2 different cars to be perfect equals but if they are going to be rated with the exact same rating they should at least be somewhat close to each other, especially if both are tuned in the same manner but this is not the case at all in Forza 3.
Take the 550 Porsche from the new DLC pack. It allows an AWD swap and it is rapidly hitting the top of the leaderboards in E,F,D,C classes on almost every track in the game. Why because the PI rating is lower than the performance of the car. Other cars do not show up in the top 100 anywhere in any class. Why? because the PI is higher than the performace of the car.
If you can not see this is a problem then either you have not payed much attention or you just refuse to admit that Forza is not perfect because it is crystal clear that the PI is not very good.
If I were to go through my garage I could give you many examples but there is not much point in it. You should see it already and if not then you likely will not.
At any rate the PI needs to be fixed.
I pretty much only race in private races (mainly organised) and have found the greater configuration of FM3 online to be a huge step up, but I acknowledge that for some the public hoppers (still fun though, just not enough variation at times) aren't cutting it as FM2 did for them.
The private racing was a very nice addition, and the options there are great as well. What they need is to activate the same system and make one of the options to be Open Lobby where as right now they only have [Friends Only] and [Invite Only]
They also need a function to allow people to search for these open lobbies similar to what was in Forza 2.
The thing is that with the public lobbies of this type you can meet up with people that like to race the way you like to race in the kinds of cars you like to drive and your circle of racing buddies expands. Sure there will be some idiots, maybe a lot of them but you have a chance to meet up with people who you otherwise would not and this is a good thing. The hoppers just don't cut it though they can leave them as well just not at the expense of the custom lobbies we once had.