hi ,bit of help please was driving home doing about 2000 to 2500 revs when i herd a weird noise ,like trying to engage gear with no clutch for a split second then a big buff of smoke came out of back of car ,still drove ok no loss of power or anything ,thought it may be turbo ,but seemed ok ,got home car still running ok no smoke or any thing ,if you rev car quite hard you will see smoke but if you hold revs from 2000 to 3000 as if you was driving normal theres no smoke ,what could it be ,2001 focus, i dont drive my cars hard or anything its was just strange