I am having trouble with cold running and now with running period. Starts fine and stumbles until warm. Changed ovp with new one-better but not much, changed O2 sensor with NGK model-initially better but now appears lean when running above 1500rpm-stumbling. O2 appears to be working. Don't have duty function meter. Stumped. Coding but do not have code reader. Going to get one. Ecu temp sensor resistance supposed to be 250 hot to 2000 cold but that does not jive with charts I have seen. 260 to 300 hot. Very inconsistent cold.