Same thing happened to me too. Took out my Ford Focus ST on Eiger, where it wins almost every time because I spent some time tuning it and it was a beast. Now it sucks. Luckily for me, I write down all my tunes on a worksheet as I tune them and guess what? For some reason, after both the system and GT5 updates, the tune reverted back to the settings I had about 2 weeks ago. Same with some other cars I've tuned in the past 2 weeks. So I changed the settings to the up to date ones and everything is fine. Of course, this means that every car I've adjusted in the last two weeks needs to be corrected which is major bs...