Download and open TXD Workshop
http://www.gtainside.com/en/sanandreas/tools/12124-txd-workshop-4-0/

Open "particle.txd" in "Your GTA Vice City Folder\models\"
and
Replace the "smoketrail" image (click "Import")

Alpha must be on. To enable it double click on "smoketrail"
and check "Alpha is used".

If you've a weak/old Graphic Card/PC double click on
"smoketrail" and check "compressed"

Press "Save TXD".