Yes you would be in Mod. It's a small step from Stock to Prepared and then a huge one to Modified. You happen to have made a modification that puts you all they way to Modified. Do you have to run E85? How do those injectors work for you if you run regular gasoline?
In Prepared, fuel injected cars get this mod:
6.2.D.9 Electronic engine controls may be modified or piggybacked, but not replaced.
You can also add a cold air intake:
6.2.D.5 The intake system upstream from the throttle body may be replaced with any material. Forced induction components cannot be changed or added (turbochargers, superchargers, intercoolers). Turbocharger boost regulation systems, either electronic or mechanical, may be modified or replaced.
Of course if you're turbocharged, you really like the above rules.
6.2.D.14 which you quoted was added last year. Prior to that addition, carburetor equipped cars had zero power adders. The current rule still gives relatively nothing as compared to what the turbocharged cars can do.
You're in CO. You should go regardless of what class you run in. RallyXing is all about having fun sliding the car around. You're already driving a Subaru so you've got a great platform to start with.