My other Civic which is a 1999 Honda Civic EX Sedan [ALL STOCK]. And for awhile its been making a load throttle noise. The noise sounds like if my muffler wasnt installed. I"m not sure if my muffler or the whole exhaust system and even something else. But everything time i accelerate the sound gets louder and decreases when i decel. I dunno, i keep really good care of my civic but this problem came out of no where. If anyone has any idea what the problem is, plz reply asap.

 
Rep Power: 308

All 3 of the 95 Civics we had for work (not same generation as yours) developed exhaust leaks right in front of the muffler. Could be similar design on 99 ??

 

I think they're similar but i'm not sure. The sound comes from the front and rear. high throttle sound in the front, low and deep throttle sound in the rear. like where the back seats are.