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5ktq afraid to rev

I've been chasing down a problem on my 87 5ktq for some time now, and I can't seem to
figure it out.  It simply will not make good power above ~5000 rpm.  It pulls hard from
3000-4500, then gradually tails off, and it takes several seconds to get the rest of the
way to redline.  I just shift at 4500, but my performance suffers.  Here are the details:
1.8 bar QLCC and wastegate spring
158,000 mi.
good WOT switch and WGFV LED blinks
ignition coil resistances good
IAT sensor seems good

spark plugs, wires, rotor, cap
michelin man
vacuum hoses
air, fuel filters

There are no codes in the ECU, and it makes 1.7 indicated bar from 2700+ rpm.  There is <6
psi backpressure in the exhaust throughout the speed range.  My ECU works fine in my
brother's 5ktq, and his gives the same problem in my car.  I had the problem before the
ECU mods.  I don't suspect a fuel problem because the engine runs smoothly with no misses
or backfires under load, so I think it may be an ignition problem.  How is the ignition
control module tested?  The Bentley gives no help.  I think I may not be getting any
advance, which causes it to gradually lose power at high speed but not run poorly.  Any
ideas would be greatly appreciated.

		Steve Burke