Now there are probably many people who will question my thoughts here. First I was under the impression that a different cam is needed in a 1.7L engine to run carbs. You will need to make sure that is done, the stock cam for F.I should not be used, ok for 2.0L though. If you are using the stock F.I pump it is way too much pressure for carbs and you really need a facet pump for carbs, that is another potential problem of getting too much gas to the carbs thus back firing. They are designed for only 4-6lbs without damaging something inside the carb. Hope this helps.
Steve
