Solutions
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David 8's post in Recirc or atmospheric? And why? was marked as the answerThey run better on recircs as that's how they are designed to.
The air has passed the maf and if its vented to atmos the ecu sees it as a leak and throws a code .... not always though.
The forge splitter lets a bit of air go and keeps a bit in to keep the ecu happy. Witchcraft I tell you !!!