Don't quote me on this but I'm pretty positive the difference between the 3.2 and 3.4 are the case and pistons when it comes to the long block. The heads are mostly the same but the 3.2 has slightly less compression. The only real difference between the two is the intake, tune and exhaust systems. I didn't feel much of a difference when I went from a 3.4, to a 3.2 with the 996 intake, fuel, and custom exhaust made with the same diameter tubing as a 996.
The seals inside the valve adjusters were going bad in my 3.4. I put the 3.2 in while i fixed the 3.4. I almost considered leaving the 3.2 in but I had lots of $$$ invested in the 3.4, so I reinstalled the 3.4. My box made 279hp at the wheels with the 3.4 and my friend mad 249hp at the wheels with his 3.2. Here's the thread
Two modified boxsters on the dyno I contribute the difference in power between us to the length of the intake runners, mileage, tune and maybe the exhaust. I have a customer who owns a shop in Dallas. He claims to have made 300hp at the wheels with a 3.2. I tend to believe him as he works on some amazing vehicles and worked for Ruf at one time.