You should be able to adjust the throttle arm on the engine so it doesn't get so close. Here's pic of my Saito 100 on my Lancair. If you loosen the set screw on the throttle arm, you can reposition it so it's not so close to the firewall on low throttle. If it gets to far, you may need to move the control horn in or out one notch on the engine throttle arm.