aftermarket parts- boost levels

i have a 89 xr7 , i was wondering if i put an aftermarket exhaust and headers on the car will that affect the boost in any way i also have a comp cam made for the supercoupe - i knowits supposed to raise the torque output nicely. but im just wndering if it will effect the boost with the mods at all

Less back pressure will give you a lower boost reading on the gauge. Go with an overdrive pulley and get it back.