The Cleave feat states that the extra attack is “at the same bonus as the attack that dropped the previous creature.” Does this really mean that all bonuses and penalties on the first attack roll—aid another, smite evil, flanking, true strike, and so on—apply to the second?
The “bonus” referred to by Cleave means “base attack bonus,” not “total bonus.” If a 6th-level fighter drops a foe with his second attack, he makes the extra attack using his base attack bonus –5 (the same “bonus” as he used for his second attack).
If you aren’t flanking the new foe, it’s absurd to claim that you’d get a +2 bonus on the attack roll just because you were flanking the dropped foe. Any lasting bonuses or penalties—such as from the bless spell, a high or low Strength score, being fatigued, or the like—apply to the extra attack just as they would to any other attack you make.