Help! Collapsing E36 air intake boot

Help anybody! I have an E36 2.8 coupe, 1999, with a cold air induction kit. The intake boot between the throttle body & mass air intake sensor is the standard BMW boot. Problem is - when the car is used hard i.e. a track day, the boot 'collapses', restricts the airflow & top end power disapears. Let the car go cold, boot pops back into shape, all is fine untill the next time it gets hot! Can't find a silicon version anywhere. Any thoughts?