An air intake system for internal combustion engine includes an intake manifold having an inlet flange and a throttle body attached to inlet flange. The throttle body includes a matching throttle body flange which physically mates with the intake flange. A friction promoting surface having a positive coefficient of sliding friction is incorporated in at least one of the inlet flange and the throttle body flange so that sliding motion of the throttle body relative to the intake manifold will be resisted.