Why is my 2001 BMW V6 325i sluggish when accelerating from standstill position? ?

Well for a start a Fiesta STi is a pretty quick car (0-60 in 7.9 secs)
It may have less bhp, but it's also a good 200kg lighter.
You don't say what mileage is on your Beemer, but it might be a bit tired if it's done 100k+, or it may well be in need of some attention.
Incidentally, it's a straight 6, not a V6.

full tuneup: eg;

spark plugs
plug wires
cap
rotor
air filter
oil change
tranny flush

etc.........................

full tuneup: eg;

spark plugs
plug wires
cap
rotor
air filter
oil change
tranny flush

etc.........................