When I'm cruising around and accelerate to 3500 rpm my car feels like its choking and I get a whole lot of black smoke. It goes away as soon as I apply more gas and pick up some boost... At first I thought it might have been the tvis opening late or something... but i was told it opened up at 4200? Any ideas? new cap, rotor, wires, plugs, not sure about the coil. Timing is dead on, I boost fine in every gear. Just wondering what is causing this.