ok so i have stock exhaust on my 96 z28 and i was wondering if i could unbolt the stock muffler and bolt in mabye a flowmaster muffler in and bolt the stock tips back on?

basically can i swap the stock muffler with a new one?

 

Only if the Flowmaster has the correct inlet diameter to match you stock intermediate pipe (2.75") and has dual outlets (cross-flow design), with the dual outlets offset to one side like the stock muffler (keeps the tips "centered" correctly), and has the same outlet pipe diameter as the stock muffler.

You will gain a lot more power with a full cat-back, than you will by simply switching mufflers. Some Flowmasters flow OK, others don't. You might not accomplish anything other than changing the sound.