>SMOKING WHEN IDLE,144000 MILES
A couple things spring to mind, the first two less likely.
****First, blow-by (bad rings). Try a heavier weight of oil.
****Second, turbo rear seal. Symptom would be a little smoke at idle, but a bigger rush of smoke when you when step on the gas; it then seams to clear up.
****Third, emissions system failure, such as the flame trap. This seems likely as a fouled emissions sytem will often generate a 'check engine' code, and is consistent with the problem being worse after a hard highway run. A clogged flame trap will build up crankcase gases (hot, oily smoke) which will escape past the piston rings or the main engine seals looking for a way out. Start with this, as it's a cheap, DIY repair. Go to volvospeed.com to check out the procedure.

>DO YOU NO HOW I COULD GET CODE READER IN THE UK
Not exactly. You're looking for an OBD or OBD II reader (On-Board Diagnostics). IPD, a US company, sells one for $179US (http://www.ipdusa.com/ProductsList.aspx?subSubCategoryID=700). Do an internet search on OBD and see what comes up in the UK.
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(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)