Trying to get the registration up to date on the AE86, so I'm required to get my emissions checked again.

Anyway took it to the emissions place, and the car failed; so I figured I'd come here and see if anyone had ideas. Here's some possible contributing factors.

-The car has been sitting in the garage for nearly a year, and just got it's first new tank of gas in just as long, so I don't know how much that may have to do with it.
-The car still has a catalytic converter, and stock exhaust system, but I did install a header last summer; although there weren't any pre-cats on the stock exhaust manifold that I can recall.
-We also reset the timing by hand, and although the car doesn't feel as quick as it used too, it seems to be running pretty good, and making more mid-range grunt than it did before. Which leads me to believe the timing is off a tooth or so, but I don't know how much that could effect emissions.

I bought a can of Sea Foam, to clean out the injectors and what not to see if that helps, but if anyone has any ideas, they'd be greatly appreciated.