1991 Toyota Celica did I do this right?

Smells problem
1991 Toyota Celica 4 cyl Front Wheel Drive Manual 178k miles

I recently did a basic tune up on my car. When I replaced the cap and rotor, there was instant positive results, but now, on the highway, there is a smell. Kind of a burning smell, but not oil or gas, it smells like the plastic form the cap and rotor maybe. Plug wires are on in proper order, i'm wondering if I did something wrong, or failed to tighten something down well enough, or if this is just new cap and rotor smell?