Motor is a 389 stroker with ported AFR 210's. My LT4 intake has been ported for a monoblade, (got it that way). Anyways from what I've researched a 58mm will flow plenty for the kind of power I expect to make. But if I'm going to run into the split BLM issue anyways, (because of the ported manifold), then maybe I'll plunk down the extra 200 for the Monoblade. I don't really understand the BLM issue completely, I know what it means, but I guess I don't understand how the IAC systems works and what it has to do with it. Any recommendations?