DaveGordon:
Does valve/ignition timing not have an effect on torque?
You can make it worse without good timing, but you cannot increase it much beyond what the current GT3 does. Likewise, higher compression ratio will help. But again GT3 is close to maximum here with current fuel quality and direct injection technology.
If Porsche focused exclusively on improving torque in the 4.0L NA motor to the detriment of some other factors, it could likely be improved by a few percent. Nothing meaningful. The RS makes slightly more torque than the GT3, but you'll never feel this (and is a result of slightly better ECU tune in the RS - where the 20hp and 7 ft-lbs comes from).
You could also slightly improve torque with better intake and exhaust breathing, but this is pretty close to max with current noise, emissions, and consumption limits.
When I talk about improving the torque of the 4.0, I guess I mean improving it beyond the RS (where the ECU does not purposely hold back performance by a couple percent).
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18 GT3 Manual, 73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 16 Cayman GT4, 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550, 79 635CSi