If it is a new installed engine and hesitating to start, it could be any number of things. The easiest things to check would be making sure the MAF sensor is installed in the correct direction and plugged in, as well as camshaft and crankshaft sensors installed correctly and plugged in. Coil packs installed and plugged in correctly would also be an easy check. It is easy to plug in cylinders 4 and 6 on the driver side coil packs since the plugs are backward and can both reach each other's coil packs. Old plastic on these connectors can often make fully plugging them in difficult, so make sure they have snapped in securely.