Strange Engine/exhaust Sound Celica -93

[loolmachine]

Recently bought my celica and not many weeks from buying, my celica started to make strange sound from engine/exhaust. We took it to a repair shop to check it out. They changed the sealing between the engine and the exhaust manifold and one sealing between the exhaust manifold and the exhaust pipe. Also they found out that one screwthread in cylinder head had ''gone off'' and they had to make new screwthreads, as far as I understood what he said. After those fixes the car worked perfectly and I even felt a clear power increasement when accelerating. After a week though the strange sound came back and i feel like the car has lost some power, again. You can hear the sound more clearly when the engine is cold and especially when you are driving about 30mph, put on gear 4 and fully press the accelerator pedal, driving window open. To me it sounds like the problem is within the sealing and the exhaust pipe/exhaust manifold is leaking somewhere. Before the repairs you could clearly feel wind blowing when you kept your hand near the exhaust manifold while accelerating when idling, so it was definitely leaking there, but now i feel nothing, yet there is that strange sound. Should I just take it back to the repair shop or does anyone have any suggestions ? Cant really describe the sound any better as I am not a native english speaker :P

ps. sorry for the vocabulary, I'm not sure if I used the correct terms describing the problems..

[gazza1286]

Sounds like the original fault related to a leak on the exhaust manifold given that your garage needed to replace a stud on the cylinder head.

If this repair wasn't carried out correctly you could try this.

Get someone to cover the end of the exhaust with a scrunched up rag while the engine is running. With the bonnet up you may hear exhaust gas escaping from the back-pressure around the manifold.

If so take it back to the garage - they should put it right gratis.