My dad has a 1997 (N) Saab 900 2.0. No turbo, just standard. He recently had the exhaust replaced at a saab garage and ever since then its not been quite right.

1. Ruffling exhaust noise at low and high revs in neutral. He initially thought it was caused by a poor fitting of the exhaust - but he had a look and it seems fine.

2. Loss of accelaration / loss of power

3. Car is not happy pulling away, but is fine once it gets going - like on the motorway. Symptoms return once car slows to 15mph or so, so its not something thats fixed by running the engine.

He thought it may have been the lambda probe (oxygen probe), but he replaced this last night, and there is only a small improvement. Obvious things like spark plugs etc have been checked.

Any ideas?