Well usually a converter company that builds a converters will loosen up or tighten up a converter if the customer is not happy for free,if its not after like a 90 day grace period.
If it was built local and is new,I'd take it back,or if the guys are really local.have them come and see for themself what its doing.
But from how you explain the matter,its too tight.Its not loose enough to keep the engine running when you put it in gear.
Is this like a 12,11,10,9 or 8 inch converter? How much money was involved with this custom converter?Some times you pay for what you get,but thats another option,Just tryin to get an idea whats going on here.
If it were me I'd bring it back,because it sounds like a "stock" converter to me
Years ago the old trick was using a vega converter,you don't suppose this is one of them do you?They would stall around 14-1800 rpms,tho,I just thinking out load.
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