@Mwenza - It is actually tearing you apart since 1991 - that's when Giggsy started playing for Man U. If you look at the banner carefully, there is a '1' on each side of 99.
On the other hand, there are people who say tearing you apart since '99 in reference to the tearing the Arsenal defense got from him in the '99 FA semi final - on our way to an unprecedented treble. The banner on the Stretford end which was submitted after request for the celebration of Giggs' 20 years as a Man U player reads "...tearing you apart since 1991".
It really doesn't matter whichever you use though. The fact is that Giggs has been tearing 'them' apart. I personally use 99 when referring to Arsenal - in tribute to that magnificent goal in 99 and 1991 when referring to everyone else.
Read some more about the banner.Never count on making a good sale. Have the purchase price be so attractive that even a mediocre sale gives good returns.