I have had this problem just recently, when changing gears 1-4 when I engage the clutch I get a poop (back fire). Do anyone know what the trouble may be? I cleaned the intake manifold and am about to put new sparkplugs in it. The car is also bogging when it gets to 3k rpm till 4k rpm. This is all normal driving. Could it be the fuel system? Oh one more thing when changing gears the shifter is real rigid and not smooth, is there any way I can fix that?