exhaust fumes

my hornet fills with exhaust fumes when i go much over fifty mph. it has a flip front if that makes any difference. all the grommets in the bulkhead seem secure and i dont think the exhaust is blowing anywhere but its still getting in. i have tried a new boot seal and taping over any holes in from the boot. also the sponge around the gearstick hole is ok. the only thing i can think of is the handbrake hole which only seems to have carpet covering it. any ideas anyone? i dont have enough brain cells left as it is!

also i just noticed there is about an inch gap at the bottom of the door seals but it seems unlikely fumes would come in their i would have thought.

It's a 100% certain that exhaust fumes are getting in through there!