Synthetic could not cause fouled plug unless you have other major problems with ring seal
If you have adjustable rockers they could be out of adjustment but it should make noise at any RPM .
My Challenger has always been open , the back of the scoops have water drain channels to take water away to the hood frame , seemed to be designed to be open , my car never had block off plates .
Cuda Hoods were never cut through so removing the plates did nothing
I agree , Chev intake , the carbs are missing a lot of parts , the list # are on the back behind the airhorn on the front & back carbs ., in front on the middle carb
They are vacuum operated carbs so there should be vacuum pots on the right side of the carbs , { left in your pix ] to pull the...
MY bet is timing is retarded too much , should be 16-18* at idle rising to 36*
Next the electric fan is probably block more air than it is moving , Factory used a clutch fan , it tightened up at low RPM to move air but released with RPM & temp to allow full air flow at highway speeds , if the...
Overall the factory system is very reliable , carry an extra ballast resistor of course & use a good quality 4 pin ECU , parts are readily available unlike aftermarket systems