Throttle body not staying open 100%

[Z06Luke]

Hello,
I have a 2004 Z06 (intake and TB are about the only unmodified parts left as far as airflow is concerned) I'm working on tuning. I noticed early on when i began using EFI Live that when I go WOT that the TPS momentarily shows 100%, but then settles back to 99.6% just a moment after that and stays there for the duration of the WOT session. Initially it bothered me, but I decided that it was miniscule.

Now that I'm putting the final touches on my VE table I'm finding that at 5600 RPM my data logs show that the manifold pressure consistently drops to 95kpa (I'm only a bit above sea level so prior to that point I see 100kpa at WOT). This seems to me that I am exceeding the airflow capacity of the LS6 intake manifold and/or throttle body. Before I go spending hard earned money on a Fast 102 intake manifold I would like to check and see how getting my throttle body opening 100% effects the symptom that I'm seeing.

Any guidance of how I might troubleshoot this?

[joecar]

DBW will not show necessarily show 100% TP.

Which pid are you logging to see TP...?

Post your log file.

What mods do you have...?

LS6 intake manifold is said to be good for at least 450 hp (maybe even 500 hp).

I take it you have the stock MAF... what about the MAF plumbing/duct...? which air cleaner/filter are you using (is it clean)...?

TP at 99% is going to flow the same as at 100%.

[Z06Luke]

I've been using auto VE, so I was logging MAP sensor, my Wideband o2, RPM, and about a dozen others. I don't currently have the data log (but all of my logs have done this). My wideband sensor went bad this weekend so I have to replace it before I can go take further ones.

I am aware that the stock intake manifold is said to be good for around 450 whp (I haven't heard 500, but all that I have heard is heresy). That's a little more than I would expect to be putting out, but I haven't been on a dyno to know for sure.

My mods:
- This filter installed by previous owner but with the factory air bridge: http://ep.yimg.com/ay/yhst-130529976527296/k-n-fipk-air-intake-kit-97-00-c5-6.jpg. Filter was cleaned recently, but I might try running a quick logged WOT pull with no filter to see what happens.
- Ported factory 243 heads w/factory valves
- Aftermarket cam (228 duration on intake and exhaust, .600 lift, 112lsa)
- 1 3/4" long tube headers
- catless x-pipe, stock titanium mufflers

Based on the dyno results from others with similar mods my expectations are more in the 425-430 rwhp range, but taking into account variations depending on dyno and elevation I figured that maybe I am closer to the 450 range that people say the LS6 intake starts to be a limiting factor.

What are your thoughts here?