According to Jeff at Rocketchip, to do anything more than a Stage 1 tune on a CDI you would need to pursue hardware mods (turbo, exhaust, etc...).

BUT, here's what you'd get with a Stage 1:

201 hp goes to 245 hp
369 ft-lbs of torque goes to 421
Vmax limiter lifted
EGR reduced

EGR elimination for off-road test purposes costs extra.

Of course, the car is fabulous as is....but for a few hundred bucks it seems worth pursuing.

I have a Stage 2 on my 98 and it's great....very noticeable difference.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 161k miles
06 E320 CDI "Rutherford", Black on Tan, 180k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 147k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 81k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife