Congrats on your classic Trek. The 400 has a sport touring geometry with longer chain stays, and combine with standard size steel tubing, the frame will flex a lot more than the 1.1. So the 400 has a slower handling, less efficient power transfer, but what you get in return is a more relax, comfy ride with better road feel and a sought after US made classic steel Trek.
To increase speed, try light wheels and tires, and ride more.