furance is over firing

Hi, I have a problem with my furance. Everytime the furance kick in and start to heat the water, the flame from the fire leak over the fire guard and burn some of the wires. I want to know if it's time to replace my furance or are there anyway for me to fix this problem. The furance was there ever since I moved into the house and I've been in this house for over 10 years.

It's probably just an adjustment or worn out part.

Some questions.
1. Gas or oil?
2. Rust holes in the guard?
3. Flue venting ok?

it is gas and it has some rust on the fire guard