engine Vibration

[ddb307]

i own a 1999 s70
i have a list of problems that i purchased when i bought the car. it is the best car i've owned by far, however there are several problems i still need to repair on top of things i've already fixed(rotors, stabalizer links, aux belt, therm and coolant flush, replacement polyurethane rear motor mount bushing, and throttle body cleaning ).
right now i have an oxygen sensor code, according to autozone, and a slightly rough idle/vibration throughout dash and front of car. i have a displaced clamp from the boot of my passenger side axle and its losing grease slowly but surely. i'm approaching 105000 so volvo also recommends i change my timing belt and from searching matthew's volvo site a tensioner renewal is also advised..when i purchased the car, i took it by a volvo dealership to be checked out and get an oil change. they advised me i needed a new oxygen heater(dont even know what this is), and a new brake master cylinder which isnt giving me any problems.
to simplify what i'm trying to have any generous person/persons help me with, i'll pose a couple questions..
what could be causing the vibration thru my dash(somewhat alleviated when shifted to neutral ) and in 1999 s70 would i have a mechanical or hydraulic tensioner on the timing belt? also if you have any advice on my other repairs i would be very thankful for it. thank you555

[cocka]

I would be checking the "front" engine mount, i.e. the one you gain access to via the r/side wheel, I had a few really weird vibrations and rattles etc. and when I checked it I found it was really badly split rubber in the mount allowing the engine to actually rest on the sub frame, took me less than 30 mins to change it with not exactly the right tools, I reckon I could do it 10 mins now. The difference it makes you could not believe, feels like a different car altogether. My car is a '94 850 wagon with 157000 kms (only had it 3 weeks or so) and it looked like it had been gone for a while. How to do it is in the repair database also on the Bay 13 site (with photos).

[White850Turbo]

'99 S70 should have the mechanical tensioner. The shop probably said that you need a new "heated oxygen sensor", just a fancy name for an o2 sensor.