i have this buzzing/raspy noise coming from the motor somewhere...ive checked all loose bolts..heat sheilds...exhaust...everything...it sounds like its comin from around the intake manifold or somewhere around the back of the engine bay...it increases with rpms....it starts at about 3k rpms and ends around 4krpms...and no other part in the rpm band...really confused..not sure..any suggestions? its a 96 rs/swapped in a b20b...