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[Chris H]

There is no point buying a Posh etc as all they are is a box with a resistor inside, 1K ohm or 1.5K ohm and it stops the cdi from reading the higher 4th,5th and 6th gear resistances so no 180khm resistance.
Regarding the post 1993 54bhp bike they are quite different from pre 93 in that the valves have less lift and the pickup is timed differently. You cannot swop pre and post cdi's over unless you fit the trigger at the same time.
The bikes are very similar as the post 93 makes up the loss of top end power by having better midrange.

[Chris H]

Its quite simple, the M-max etc only gives the 1Kohm no matter what gear you are in, the cdi thinks it is always in 3rd and does not cut the ignition. You could run any of the lower gear resistances, im not sure if they give differences in ignition timing, the only way to test would be to run the bike on a dyno for each resistance and see.
Regarding the 53/59 hph bikes the 6bhp is not missing, its just simply been moved down the power, more mid less top end.
If you go to the track and take a look at 70+ hp 400cc race bikes they tick over at 3000rpm as the bottom end is completely flat in the serch for outright bhp, they simlpy will not tick over due to making all the power after 10000rpm.

[Chris H]

Not sure where you get your info from but the VM and VP are not the same spec.
From the official Suzi manual-
GSF400VM inlet opens lo-18 deg BTDC, hi-46 deg BTDC, closes lo-38 deg ABDC, hi-66 deg ABDC. So in hi mode the timing is 292 deg.
GSF400VP inlet opens lo-14 deg BTDC, hi-38 deg BTDC, closes lo-34 deg ABDC, hi-62 deg ABDC. So in hi mode you would get a smaller valve timing of 280 deg.
There are lots of small differences between the two engines that do not detune the motor, just move the power lower down the rev range.