Complex sentence: Although the duo nominally had already given their final concert on New Year's Eve 2003, they reformed again to perform as a warming act for two Toto gigs: the first on August 17,2007 in Oulu and the second August 18,2007 in Tampere.
Split into simpler sentences: Although the duo nominally had already given their final concert on New Year's Eve 2003, they reformed again to perform as an opening act during two Toto gigs. The first tune on August 17,2007 in Oulu, and the second on August 18,2007 in Tampere.