All upgrades are maxed out but...

I have maxed out all the upgrades of my Sauber and yet only reached 5th in the performance table. I can't upgrade any more so I can't compete with the four teams ahead of me. The top team is waaaaay out in front (Williams) and have become pretty much unbeatable. 

Is this right? In other career modes I've seen on Youtube - Ben's for example - he took Manor to the top of the table. It is now impossible for me to do this.

Any thoughts? Advice?

Cheers all