You're probably looking in the range of 40 HP or so, if these are the only mods you make. Other mods can have affects on one another.
If you do these mods, go ahead and slap-on a hi-flow cat converter as well. It'll be worth it.
Long tube headers and a good catback exhaust. get magnaflow or a flowmaster
cheapest way is cold air intake, after market performance exhaust with xpipe, headers and catback mufflers, new plenum, throttle body, performance chip, performance pulleys, and many more. What kind of car?
Let's say you have a stock 2002 Trans Am. Full aftermarket exhaust (headers, y-pipe, catback) would put you a little over 50rwhp. Headers alone are 25-30hp. A dynotune is highly recommended after installing full exhaust to maximize performance gains and to make your car run smoother.
Headers. Because less or no exhaust back pressure.
all engines have exhaust headers but the headers your thinking of are aftermarket performance headers, the ones on the 440 from the factory are made of cast iron.
Turbo or Supercharger + K-PRO chip for ECU + Full catback exhaust + headers +intake upgrade+ K-PRO tuning job.
Header or headers are a high performance version of an exhaust manifold
The answer would be "No, you don't have to". If you installed exhaust headers to improve performance then you might consider if your current exhaust system compliments the headers. Headers are designed to help evacuate exhaust gases and minimize back pressure. If an engine has exhaust headers that collect into a small single muffler and pipe then the effort is somewhat defeated. BUT, if the headers are installed for the "cool factor", and there is nothing wrong with that, then go ahead and use the stock pipes or as much as you can.
By adding a dual exhaust and/or exhaust headers either short or long tubes for sound and performance
You could supercharge it or turbocharge it....As far as now...stockwise...Go for the CAI, full on catback exhaust, short throw shifter, grounding kit, performance tires, spark plugs and wires, Twin-Fire CDI Ignition, flywheels, and then you have headers.
Headers help the engine breathe better thus better performance but the rest of the exhaust system needs to be included.
It is recommended to remap most engines after installing performance parts. The benefit of remapping is getting the full benefit of the new exhaust headers.