More Boost but not more power?

New here and looking for some help. The short version is I swapped pullies and am making 4-5psi more than I was before (15psi now 10 psi before) but my trap speeds and e.t. are virtually the same.Long version is as follows.

Anyone have any ideas on the following?

Running a vortech V1 Charger on a 2.8 6Cyl 10:1 compression motor.
air to air FMIC
Haltech E6X
42lb injectors W/Bosch inline pump
With 10psi@7k I ran 112.3 mph (Centrifugal makes max boost at max RPM that’s why I listed it this way)

Swapped to a smaller pulley, see anywhere from 13-15 psi at 7k (Separate belt slip issue)

Best MPH with pulley swap is 113.65

Thought maybe my 2.5 exhaust was choking the car down so I went to a 3” (no cat on either one)

Still ran 113.5 mph!

Car has aftermarket NA cams (on the larger side advertised as 268’s)

Was really expecting to see traps jump to 116+

Both setups were street tuned with a wideband O2 sensor.

10psi pulley was tuned to ~11.8 AFR and ~27 deg timing

13+psi pulley tuned to 12.2 AFR and 24-25 deg timing (Lowered timing because of leaner AFR and higher boost pressure)

Air intake temps are stable and just about the same for both boost levels (larger air to air intercooler helps :D )

Impeller speed calculations have me under 50,000 rpm at redline so it shouldn't be an issue with overspeeding the charger.

So anyone have any thoughts on why I’m seeing more boost and not really anymore power?

Two possible scenarios a friend and I have:

Cams are too big/too much overlap and not boost friendly (If that’s the case why did they work fine at 10psi?)

Issue with valves hanging open at the higher Intake pressure? Maybe the springs are too weak to control valve events with the extra pressure on the back side?

Motor is older but showed exceptable static compression test numbers as well as leakdown numbers. Leakdown was even across the board and past the rings in all cases and was not major enough to worry about.

This motor with a 60-1 TO4 turbo (similar compressor map to the V1) should make ~300whp @10psi which is exactly what trap speed vs. weight calculations show I am making. At 15psi from the 60-1 this motor should be making ~360-370whp. I would expect the Vortech to make similar power numbers minus some additional losses from spinning the charger. Even if it doesn't make that it should make enough additional power to trap more than 1mph faster.

Any help would be greatly appreciated

I think you arent seeing a gain because you also removed 3* of timing. What type of fuel do you run?

Running 92 pump gas. I am going back to stock cams and will see what they do.

I agree the reduced timing could be part of the power loss but I don't think I am willing to push the timing much further while tuning on the street.

I have tried asking around about timing curves for a centrifugal charger on other forums and haven't gotten many replies. It seems whenever you ask for help on making a s/c go fast people just say go turbo. Hopefully I can find some more info here :D

Have you thought about trying methanol to get lower ACT's and a more aggressive timing curve?

While I realize that many people have ahd great sucess with methanol injection if I am going to bother injecting anything it will be a shot of nitrous.

I will be going to the dyno sooner rather than later to dial in the tune. Maybe all I need is a little more timing.

Have you put the car on the dyno to see what kind of HP it is actually making? Also, do you have a chip?

As stated in the original post I am using Haltech E6X so I have full control over fuel and timing.

Still waiting to hear on dyno time - There are a bunch of Dynojets locally but I know someone with a Mustang about 2 hours away. If I am going to bother putting it on a dyno I would rather use an eddy-current load dyno and get a good tuning session in. I am fairly confident though that the power level is right around 300whp@10psi. I know the cars weight and its trap speeds were very consistent at that boost level. The HP calculator I use seems to be pretty much dead on, at least at the lower hp/slower et levels.

I have gone back to the 10psi pulley just to try a couple of things at a boost level I know was giving good results. Unfortunately this heat wave will probably postpone both track and dyno time a little bit. Not trying to kill myself or the car :)