Agreed, the butt dyno always reads higher since you 'want ' to know you just wasted all that money on hp gains. In theory on a fresh engine, or one will lower miles it would produce a decent gain. Header, intake, high flowing cat, decent muffler, then some injectors, and TB to liven up the extra airflow. THink of the dolar spent?
Now you have spent enough on a tired engine to have almost rebuilt the darn thing.
84 xj 350tbi, sm465, 203/205, 60/70. links and other junk.
what size sawzall blades does it take to fit 40's?