Having gone from aircraft plugs to auto plugs back to aircraft plugs and from mags to EI back to mags, my perspective is either works quite well. Whether or not the performance differences are all that spectacular is debatable. After all, the Lycoming is a slow turning engine and old plugs and mags suit it quite well. I do believe the CAFE flight testing does confirm up to 8000', mags and old plugs may be better.
I like the REM37BY's because they seem to last forever. In fact, the original Jeff Rose EI system recommended them. Other EI systems go with various auto plugs, none of them last as long as the 37BY's.
No question, auto plugs and EI in modern engines is the way to go and maybe for engines highly modified such as Klaus Saviors. But the jury really is out on whether they work better in these old technology engines for the average guy. The plugs are cheaper, yes, but they also have to be changed more often. The jury also is out on whether or not an EI system affects Lycoming engine life. We know for sure a pampered engine with mags will easily run 2500 hours but we do not know if it will make it with EI due to much different temperature patterns within the combustion chamber.
...just my 2 cents worth on the subject and it may not be worth that.
