I made the same thing with Ferrari And Alonso. In both conditions (with and without timeshifting) AI sucks.Ok did some laps on Spa, short qualify, legend difficulty, with Alonso and one of the best set-ups on RD for Spa. I drive 1:50.4 which is pretty onto my limit (not always flawless too). I could drive a 1:50 maybe. The fastest time was 1:48.7 set by Massa. Now I will do the same for Monza. Tbh, AI is too fast in qualify on each track almost. And it's not that I'm driving like a noob. Anyhow, will do the same now for Monza.
So, try drive on Professional difficulty