Gunson Gastester G4125.

Rotax 914 wants minimum on leanest cylinder between 4 and 6% carbon Monoxide when creating "war emergency power" (above 108% power).
This means with 100LL, High test Mogas with 10% Ethanol or High test Mogas with 10% or more Ethanol and for high altitude flying a pint or so of Isopropyl added in hopes of keeping water in solution.
I will verify with modified intake track on our 914 (intercooler added) thing is rich enough. On old airbox Rotax wants higher pressure hand in breeze adjusted. Think new style hand that I have adjusting on will not make too much a change, if lean will go to main jets.
Idea is to measure pressure going to Gastester from exhaust from my car when used as it is designed. Then will plumb a fitting ending with perhaps 1 foot of copper tubing coming from each EGT plug, then run plastic tubing into cockpit. I will create a leak in plastic tube, trying to make it at a low point so water leaves tube and only creates design pressure that is run to Gastester in cockpit. I can pretty easily remove Ultimate Ventilator articulating deflector and run tubes in through the opening. I ran my plan by Jay Smith and Russ Haggerty and both thought plan sounds feasable. Also ran plan it by Ben from Automotive Tools 4 less 866-251-4267 and he thought plan sounded reasonable, he mentioned it may be a good idea to keep temp of exhaust gas going into Gastester below ~150F (pure guess though).
There will be some exhaust being expelled into cockpit, not much though. Will monitor careful.
Y10-03-11

Update:
According to older bulletin Rotax wanted 4 to 6% above 108% power, Install manual Y08-07 says 110% to 115% 3% CO and 100% to 104% 1.5% CO. I will still probably taint towards higher numbers.