need opinion on exhaust

i have a 94 EGT and last year i took it to a muffler shop and got a 2 1/2" strait pipe exhaust on it and an after market muffler. it's loud but i still have a manafold on it and i was thinking about replacing it with a header. i was wondering if it would be worth the tickets or if it would make much of a dif. in sound and power? and will strait pipe hurt anything in the motor? when i let off the gas it make a strange rumble/poping sound. just wondering if that is normal.