[amigo-2k]

The vibrating type noise could be the timing belt tensor, but I haven't heard of any +98's having that problem (and you only have 70K).

Most folks around here change the timing belt at 100-120k. And most note that the belt looks to be in good shape when then pull it out.

If you still have the OEM plugs it would be a good time to change them (steel treads, into an alumin block do not like high mileage).

also you don't have plug wires (you have coils over each plug).

It could be a plugged EGR or Cat that is causing reduced power.