There comes a point where the equipment being used is in stone and you just simply ignore what they are and proceed with the build accordingly. Knowing the intake and exhaust is curtailing power and hurting the build, you redesign the camshaft and make the best possible choices elsewhere on the build to help as much as possible.
The F.A.S.T class of racing has proven this. Since he is not going up in cubic inches, the OEM parts are not taxed as much like a big stroker would tax the OEM parts.
Making concessions in camshaft profile and other parts of the engine because of the OEM intake and exhaust manifolds only kills more power and makes for a weaker engine.
You must pay attention to the duration @050 and the overlap (LSA) of the camshaft to make better power than grabbing an off the shelf camshaft. IN ANY APPLICATION!
If you just want to just press the easy button and grab a off the shelf cam, then be happy with your results. When you get a pasting on the street, blame yourself.
A wide LSA is a torque looser. While it’ll give a higher vacuum reading and idle nicer, ask yourself, would you throw away 30 ft. lbs. of torque or more just for a smooth idle?
For a described car the OP has given, a wide LSA is not only the last thing I’d do but I also would make sure the cams profile would stay aggressive and work in my desired RPM range I’m looking for. Lack of vacuum hurting power brakes?
Add a vacuum pump. Double rubber mount it at the front of the car under the battery tray.