Carbed 914 Problem Options

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I am doing some work on the 914 that I built and sold last year and have run
into something that has me stumped.
The car:
2056cc
WebbCam #86 grind (I think)
IDF 44s
Stock valves w/heavy duty springs (bus I think)
Carbs matched to intake, intake matched to heads, no porting, just 'cleaned
up'.
050 Dizzy w/electronic ignition (Compufire)
Taylor wires
Bosch Copper Plugs (new set)
MSD 6AL
Facet Fuel pump
Facet Pressure Regulator (set at 2psi)
Car has been running great for the past two years, then at last months
autocross, it started acting as if it was running into a rev limiter (goes
'soft') at about 5500 rpm instead of at the 6500 rpm 'pill' in the MSD box.
I first tried removing the pill which should remove any MSD induced rev
limit. Problem was still there. Checked all wiring and all looked fine, even
screwed in a new set of plugs at the autocross. Still fall on it's face at
5500 or so. Below 5500 the car is flawless.
Fast forward to this week. Took the MSD box out of the system, problem still
there and I noticed that it seemed to be intermittent; sometime it would rev
to 6500 the next time it would only go to 5500. Next I removed the CompuFire
and installed a new set of points. Problem still there. Installed new cap
and wires, no change. I next checked all the fuel filters (one before the
pump, one before the regulator) all clean, but I replaced them anyway. No
change in performance, still goes soft. Took the tops off the carbs to check
float bowls; all clean and levels are correct. Removed and cleaned all the
main and idle jets. I installed a new fuel pressure regulator and fuel pump.
No change. The car idles great and runs great up to 5500 rpm or so.
The odd thing is it feels exactly like a soft rev limiter.

Ideas?

TIA

Mike Allen
San Antonio, TX