The number 6 cylinder is not firing.
Things I've checked are:
the fuel injector
spark plug
spark from coil
fuel pressure
compression test
valve spring
couldn't detect any vacuum leak
These all checked out fine, but the no. 6 just won't fire
any idea what it could possibly be
thanks

If you've correctly tested spark and compression and they are ok (within reason) that leaves only one thing, Fuel. Just because the injector is spraying that doesn't mean it's good, I've seen injectors get clogged, gummed or just erratic. Try swapping the injector to another cylinder and see if the misfire goes with it.