I found my MG66 prefers to be a tad richer than my 7 port at the top end..flush or just an hour in from flush..a hour + or - seems to make a big difference..and the same at the bottom end..just an hour in on the lsn changed my runtimes from 8m45 up to 9m50..I'm expecting 10m30 or more once I really start to race tune it..especially with the ceramics in..but for anyone tuning one of these..use a light hand.tiny adjustments are all that's needed.But once it's right it holds the tune forever and idles better than my car..