Does anybody have any experiance with the MSD 6A or anyother brand of capacative discharge ignition and the distributor type ignition system on the 4AGZE?

My twincharger set up sees some decent boost pressure (about 18psi) and it has never really felt that good at higher revs. It has great midrange, but the top end is pretty average.

What are some good indications of an igntion system that isn't coping with high end loads?
A particular noise to listen for?
Mixtures richer than to be expected (I have an Innovate wideband AFR meter)?

What plugs are most 4AGZE guys using?

"Stick it on a dyno" isn't on my list of things to do, as the nearest dyno is owned/run by a bunch of wombles who displayed some amazing ignorance about force fed engines.
The goose couldn't even scale the graph so we (mates car on the dyno) could see what it got to once the line appeared from behind their big logo.