Thankfully, this isn't a P-port, it is a stock-timing mild street port. The EGT is seldom over 1500F even at WOT (although I haven't had it on the dyno since I installed EGT thermocouples).
You may be speaking to j9fd3s (who has a P-port) as you can probably tell from the pictures that mine has the stock intake manifold and is therefore not a P-port.
Anyway, I did some testing after adding this:
The waveforms changed considerably with the addition of a collector.
Before I show them I should explain that 100 mV is 0 pressure and these transducers read as low at 1.5 psi negative. Some of the pressure seen below is going to be significantly negative. This means that the headers are working.
Most headers require a collector for proper scavenging.
Anyway, here is idle. Please don't let the weird waveforms confuse you, the engine is only firing once every 60 ms (acoustic and sonic properties of the headers/chamber are causing the rest):
Here is revving from 2500 - 4500 rpm:
Here is revving from 3000 - 5000 rpm:
Here is revving from 4000 - 6000 rpm:
Here is revving from 7500 - 9000 rpm:
Bouncing off the rev limiter:
I will do a writeup of each change when I am done. Right now, I am building the exhaust system piece-by-piece and re-collecting data each time.