one thing you gotta remember, is each car is different, where some people may only need CAI, Exhaust, PCM, to run that.. others will need a whole lot more, including ported manifolds or headers, and rockers...
Depends on your car. You are flirting with trouble though.. if you come up with "pie in the sky" dreams to run something smaller than you are capable.
I had to run rockers, ported manifolds, exhaust, PCM, and other things to run a 3.25. And even then, sometimes I see knock.
It all depends on your car. Best thing to do, is to get an autotap, with what you got, and that would give you an idea. Most people are seeing knock with only a 3.4. Going to a 3.25 at that point, would mean that you will soon need some major work on your car, when it blows up.
Be careful, and mod safely. Get an autotap.
John