Subaru Legacy Mechanical problems(possibly blown Gasket)?

I have a 1997 Subaru Legacy which seems to be running quite rough. The way it drives is comparable to when my last car had a blown Gasket, but not nearly as
bad. I had thought it was a potential blown head gasket, until I realized the timing belt was soon due to be changed. I did some googling and Some of the symptoms of a needing to be changed timing belt was similar to how my car is running:Mainly being a ticking sound, slight misfires , but no oil leakage I can notice. When taking off in first gear, the car takes a while to pick up even if my foots hitting the floor on the gas, it does eventually pickup, but it's quite rough and driving the car overall can be quite 'jerky'. The ticking noise does often occur. A few weeks earlier the car wouldn't start up properly and was blowing petrol smelling smoke out(hasn't happened since).My question is, is this likely due to the timing belt needing to be replaced, or what could it be? Any help/Hypothesis's are welcome. Cheers.
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