That one I can answer. The early 300e is limited by engine speed. The rev limiter located in the fuel pump relay is set to shut off fuel supply at the engines redline, which i believe is 6200 rpm. You can change the relay with one that would let the engine rev higher but there would be no point to do this without an engine that could take the load. In other words, you would want to beef up the engine to handle the revs.
Good Luck!
Adam

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320