Maybe someone can help me out here before I pull all my hair out. I have a 68 C-10 pickup LS Swap. I have an issue after you let it sit for 2 or 3 days it takes forever for it to crank and then when it does finally crank, it runs like crap for almost 5 minutes. It has a "Tanks" fuel tank under the bed with the corvette style regulator/filter with a return line to the tank. I just put an inline gauge at the rail and have 58 psi when I turn the key to the "on" position. I have tried changing plugs, regulator/filter, maf, and everything else. I had a tune on it from a very reputable shop but no luck there. But when it warms up, it runs awesome. It is a fairly stock LS with a fabricated sheet metal intake on it but that is about all. I'm thinking it is a mechanical issue and not a tune issue but not 100 percent sure. Not sure what to do here?