Mazda Repair: 98 323 protage, exhaust sound, dident

Question
little 1.6 mazda has been an excellent car.
just recently it has started to lag/surge when taking off from stop or taking a corner in 2nd.
there has been like a hole in the exhaust sound for a few months - although i have had the car up on jacks - so far have been unable to find a hole. the sound tends to come from somewhere at the front.
can you please point me in the right direction.
regards

Chris

Answer
dident say if it was a califonia or federal emissions vehicle, not sure how a exhaust leak would cause lag/surge. either the manifold is cracked, or the pipe below it..  i've seen both go bad many times. as far as running, check the ait tube for any cracks or rips, also check the fuel regulator