TPI is no good after 4800 rpm's but I found restrictions can really choke it off.
Intake and exhaust on my truck TPI were restricted and robbing a bunch of torque and HP.
Just seems smaller valves would do the same.
Second entry down shows the difference in dyno pulls after removing restrictions. Maybe these heads are a totally different deal, but in theory restrictions cost torque and HP.
TPI DYNO PULLS