Without having to butcher your rifle , I’d have to say the kit from FX or possibly the polish plenum if they are still available. I have the polish plenum from the second run he did. Great product, fit and finish were good. But the only thing you get is the plenum. I believe the FX kit comes with other upgrade parts. The plenus that were inserted into the rear gauge hole needed the hole to be drilled out and tapped for better air flow , not to mention having to modify the valve housing ,again for flow.