What is your goal for switching to headers? Which headers long, short , 2.25” 2.5”, adding h or x-pipe, increasing exhaust tubing size from stock? What mufflers do you have - flow rate (how restrictive are they)? Just switching to shorties and keeping everything else the same you might gain a few ponies, long tube maybe a few more. To optimize gains you really have to plan from carb to tailpipe as going with too large a header can result in decreased performance. What is your budget as headers can range from fairly inexpensive ie Hedman to expensive McJack. On a stock system going with McJack’s would not likely add much of anything over the much less expensive Hedmans. Any seat of pants increase you might experience would likely be more psychological. Your neighbours would not be aware of a simple header swap.