Some small things that you can do to help enhance what you already have.
Iridium Spark Plugs-uses less energy, better spark (better spark = better combustion= improved engine performance
K&N Air Filter KA-2586-(drop in)
87 Octane ethanol free gas- (if you can get it)
More shims- Depending on the size (thickness of your shims) you may what to add one more. (For example 1 Factory Pro washer is about 0.54mm thick. I have two washers that mic @ 1.53 mm.so you can either move the needle up 1 mm with 2 Factory Pro washers or 1.5 mm with another brand 3 mm washer. 1 washer really doesn't do much.)