Welp, I figured out one huge bottleneck my car has. My OEM intake filters were
disgustingly filthy. I mean
charcoal black, as dark as the bolded text. I have no idea why after 15K miles the filters were in such terrible shape, but they were also covered with bugs (dragonflies even), and so air intake was obviously suffering quite a bit as a result.
This car doesn't have a standard drop-in filter, so it required the removal of the airbox to get to the filter (although I discovered a workaround). So I first got rid of the bugs and went to AutoZone for some K&Ns at $55 each.
After I installed them, I noticed something odd...the air inlets for the intake are facing upward...not down, not forward, but upward. They're drawing in air from the top. So I looked at the plastic shroud cover that I took off:
And I look underneath it, and it has these reaaallly tiny and narrow inlet ducts that guide the air to the airbox. And I immediately thought what a terrible, restrictive design, and then realized it's done to also muffle the shit out of the engine. And I was right. So I left it like this:
I took that pic just now, after about 80 miles of driving. The sound of the motor has dramatically improved, as this has effectively eliminated a lot of restriction - the motor would whisper before, but it growls and howls now. If you've ever done an aftermarket intake on a motor that had more than 3.0L of displacement and loved the sound difference, then you know what I mean by the change in tone - it sounds beautiful.
Most importantly, it's also added a fantastic surge of power that is now consistent all throughout the revband. Which leaves me extremely pissed that I didn't do this before, because I dyno'd the car with old oil and fucked up filters, and a chunk of plastic choking the intake.
I know if I went back to the same dyno I'd have put down 380+WHP stock and 400WHP with the tune. It makes sense now why the car did not respond to more fuel when it was being tuned - it was actually losing power. It couldn't breathe enough to justify the mixture.
Oh well, I've got a custom exhaust that should be put together for it soon enough. It'll breathe more, and then I'll dyno it again. All I know is that this car is an animal and I love it.