Absolutely, you must get the right distributor. The lambda control distributor expects and needs lower chamber regulation via a electronically controlled frequency valve (controlled leak). By shutting off the circuit you bring differential pressure to zero and are only getting it started by in effect over enriching it. Problem is that without control the only way for proper running would be to reset the mixture to every airflow quantity; not very practical.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician