A few year back I did some upgrades to the 440 in my Duster. I added Edelbrock heads, Mopar .557 cam, new Holley Ultra HP, and replaced my Schumacher headers with Pro-parts semi-fenderwall headers. Since this upgrade, after driving for a while and shut the car off it cranks and cranks but will not fire. I have to let the car sit and cool down for 15-20 min before it will restart. I have no idea what the issue is. I never had this problem before tearing the car apart for upgrades, it was always dead reliable and fired up with the twist of the key. Ive tried insulating the fuel line and checking timing and all other diagnostic stuff. My MSD is mounted under the hood and is 15 years old now and I'm wondering if it is cutting out when it's too hot or if I'm having a fuel issue. I have a mechanical pump with a regulator. I'm at a loss and looking for suggestions. Thanks