Sorry to say bro but there is almost a hundred lb difference between you and your buddy, don't know you so I won't say your fat, just big boned? Or a giant. Anyhow your weight and the 100+ difference between bikes depending on any mods you have done on your bike to lighten the load would certainly make the advantage tip more toward your buddy.
My suggestion is to uses the losses as fuel to get the weight down on both you and the bike, you'll feel better look better, run faster and all he will see is tail lights.
Case in point, raced a guy with my son on the back (Bad parent I know! But couldn't lose in front of my kid, as he was egging me on) he weighs about a buck forty and I'm 215-220 so my weight at that time is about your current weight plus
75-100 lbs less the weight loss done to my bike, exhaust ect.
He's getting his own bike in a few months so he will be the last guy to ride with me!
The roll on from 60 was terrible compared to when I'm riding alone, instead of the normal "oh my I've been shot out of a cannon this is unbelievable acceleration I can hardly hold on! This is so freaking awesome!". It was like wow, I'm passing him but this isn't normal, is something wrong with my bike?
My bike is lightly modded Two bros exhaust, juice box pro couple of others, but the weight difference is a huge factor.
Loss of weight will cause sudden loss of friends on a Busa!