A 98 has a mechanical throttle. 99s have electronic throttles.
Quick check under the hood tells you if you have a throttle cable.

Also, at some point 98s went to a new mechanical tensioner for the
timing belt. It extends the life to 105K miles (instead of 70K).
The technical service bulletin 2210015 has the details (ask a dealer
for a copy next time at a dealer). The TSBs are also online at
www.alldatadiy.com ($25/year to subscibe) and the TSB says in car
with this serial number, or higher, has the new timing belt:

Engine serial no.:

S70/V70/C70 1266128-


www.alldatadiy.com has a lot of good info on our cars and if you
are a do it yourslefer I recommend it along with the info at
http://volvospeed.com/bay13.htm.

By the way, my 98 T5 has a 1/97 build date.

Ray