Volvo Repair: 1991 74oL turbo wagon, bob fitzsimmons, rear muffler

Question
I bought this car in February, and the shifting seems to be annoying. When I go up slight inclines, it downshifts automatically. Also, the air-conditioning doesn't seem to be that strong.
ONE MORE, what would it cost to have the muffler and/or exhaust system replaced?
(This is my first Volvo, and it is a good car, considering 168,000 miles)

Sincerely
Bob Fitzsimmons

Answer
I would have the shift cable checked it may need adjusted.not sure what you mean by strong on the A/C.if it does not seem cold enough it could be low on freon.exhaust system is about 250 dollars I believe and labor about 2 hours to install.this would be front and rear muffler,pipe between them,tailpipe and clamps.not catalytic converter or dwon pipe from the turbo.