If you want more speed then you need to go up in pitch. This is akin to shifting up a gear while driving your car. You'll get more speed on the straightaways but will lose some power for climbing hills.

The control line stunt pattern is full of hills to climb.

What is your lap times? I usually clock the model in level flight for 10 laps then divide by 10. Anywhere around 4.8 seconds to 5.0 seconds per lap is a good starting point.

You can also go to shorter lines to "increase" lap speeds without having to increase the speed the model flies. The Top Flite Tutor II with a good 40-46 engine should be flown on 60'-64' lines. You'll need .015" diameter for .40 engines and below while having to drag the heavier .018 lines around for anything larger than a .40 engine. The weight and drag of the larger diameter lines *does* make a significant difference.

If you currently run a 11-4 prop and it seems too slow but pulls the model just fine, go to shorter lines. If you're insistent on going faster then change the prop to a 10.5-5 or 10-6.