I own an 84 gs 12a n/a. when started, as you rev in neutral, you can hear a distinct whistling. also, in decell in gear the bitch starts backfiring bad, not much smoke in general. and when you get on it it bogs in higher rpms... apex seal?? Have accel coil packs/plug wires, rb header with custom fabd collector into 3'' pipe into flowmaster super 40. running valvoline semi synthetic highmileage oil, and premixing with royal purple synth 2cycle oil 100:1

also is it possible to check compression with normal non mazda specific gauge???

thanks.