I have an 87 Shelby Z with the following mods:

Ported head
3 Bar Map
+40's (Using DSM injectors)
Shel Game Cal
Grand National turbo (essentially a S70)
3" Exhaust
8.5mm Aurora Wires
New Cap
New Rotor
New plugs (a range colder) gapped at .030
FMIC
RFL BOV
Walbro 255
New rubber fuel lines under the car and under the hood
New fuel filter
Vacuum Block
52mm Throttle Body (intake neck ported to match)
TBI Cam and Followers and 3* of advance using offset cam key
PT Lifters
Ported Exhaust Manifold
Ignition timing set at 13-14*

The problem I am having is that I have a fairly inconsistent misfire at idle as well as a specific misfire at 5500 RPMs. The misfire at 5500 happens in both first and second gear at 5psi and 9-10psi. I have verified cam timing using the timing light trick, although when it starts to misfire at idle, the "standing image" of the cam gear seems to rotate towards the firewall so its no longer in line with where it should be. It goes back after the misfiring ends. My wideband is not functioning at the moment, but when it was, I was getting 11.3:1 at WOT at 5psi.

So far I've tried resetting cam timing about 3 times, ignition timing has been at 12* and 14*, tried a new coil, gapped the spark plugs from .035 to .030. Plugs display no speckling and haven't had so many miles on them as to turn them tan. Nor are they black with soot/oil.