l wanna upgrade the impeller for better low end acceleration, without top end loss.what would be the best impeller to up grade to?also after takeing a sharp u turn it lags with 2 people on it and take a second or two to plane out...what would cause this?thanks.

The skat-trak swirl impeller is ur best bet
since they r made of thin stainless steel that flexes
to a lower pitch when under pressure & then flex back to the higher pitch at higher speed thus increasing top speed.
the lag u speak of is due naturally to the loss of speed associated with taking a turn, especially with the added weight of a second rider.
FYI: that skat trak impeller will set u back about 250 bucks
but its worth it, especially if combined with an aftermarket
high compression head(about 50-100 bucks on ebay)