Invariant mass plots are shown with and without shower shape substitution being applied with Data Driven Maker (thanks Ilya).

Data Sample  ->  2 pion events exponential in Pt starting at 5 GeV, and thrown at phi=[20,40].  There are 10000 events total.

Figure 1: Generated distributions for half of the events in the data sample (i.e. 10000 pions).

Figure 2: Invariant mass with DD Maker ON (red) and DD Maker OFF (black)