I would first start by disconnecting vacuum from the distributor and plug off the vacuum line. If the problem goes away then you know you have an issue with the vacuum circuit of the distributor. Also first verify that you actually have vacuum at the hose to the distributor by simply checking it with a mechanical vacuum gauge.
You may also have a fuel filter issue this is simple to check by removing filter and trying to blow air through it with your mouth in the direction of flow. If you are not able to easily pass air through the filter, then considering you can only get about 7 psi from your mouth the pumps will have a hell of a time passing 60 + psi through the filter. Solution. Replace fuel filter. Unless you already have.
One more possibility is the fuel injectors them selves. If the engine you purchased was sitting for an extended period of time there is a good chance the injectors could be partially plugged up and have poor spray patterns. You could do a fuel injection service or add a GOOD in tank fuel system cleaner like a commercial product such as BG chemical companie's "44K". If you cant find this product and you need some I can help you there. PM me, the stuff is a miracle worker!
Hope this helps you out............................C
