Posting this up on behalf of a mate of mine who's also on here, and will no doubt stick in his 2 cents
Apparently no-one beleives him that you can instantly gain 5kw+ on the dyno by just removing the airbox lid.
I was getting a touch up on my tune this week and after it was finished and dynoed, I got another run done with the airbox lid taken off.
Nothing else was touched. These runs were literally back to back, same dyno, same day, same tune. Only difference was the airbox lid was removed for the second run.
As you can see, with no airbox lid (the blue line) there is a clear gap over the entire graph. More power everywhere, with even more top end.
It also affected the afr's as you can see, and was knocking a bit at the top end. A re-tune would be needed if you were to run with the lid off all the time.
So as you can see, it DOES increase power....happy Justin?