Hi - I dont have an Evolver yet (being delivered) so this is just a guess.
Try setting the Cutoff frequency to zero then retry the modwheel (routed to cutoff).
Normally mod routings like this are cumulative. So, if you Cutoff is already set to 50% the Mod Wheel will only add its value to this setting. Obviously once the mod wheel gets to 50% the sum total is now 100% so any further increase in the mod wheel will have no effect.
Obviously I can't try this out so sorry if it is incorrect..
Good luck,
Paul
London
www.punkdisco.co.uk