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If you keep reading enough on internet forums, you will probably keep reading the same response from self proclaimed experts (i.e. Rennlist) that the 964 injectors are barely capable of supporting anything but a stock motor, well because heard/read that themselves somewhere from a guy who was a meister (hey gotta sell a Motec upgrade right?). The reality is that with hod rodded 3.8 combined with a modified exhaust (like header and an open exhaust) and cam like the 993SS, the injectors only start maxing out at full throttle after 6200 rpm on, and then you'd see AFR's around 13.4:1, where normally I'd ideally try target 13.0 to 13.2
I have dyno tuned more 964 3.8s on the dyno than I could ever count, both on chassis and Superflow engine dynos, and in some instances with injectors replaced with 993 ones. In the end what works every time and what I recommend is if you go beyond a basic 3.8, in other words, if you add a cam, then all you need to do is modify the fuel pressure regulator by 0.5 bar, (about 7psi), or you can get an aftermarket adjustable regulator. But modding your stock regulator costs nothing and looks factory. The net results are that the injector duty cycles come down to basically what a stock 964 run at, so any concerns of the injectors being pushed to max are not a concern anymore. If you build a 3.8 with the stock cam, there's no need to do this. On 3.8s I tuned where the injectors were changed to 993 injectors, such as engines built by Mirage or Singer, the results were very mixed and never consistent, so I'm not a fan of changing injectors. Keep it simple.
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