Roofit time consuming Range change

Roofit and RooStats
5

This is the part where I change the Range:

    varx.setRange("Full",fMinIM1D,fMaxIM1D);
    varx.setRange("1",   fMinIM1D,  1.045);
[...]
    vary.setRange("8",   1.000,     1.040);
    RooFitResult* FitResults;
    if ( fRangb )       FitResults = fMod.fitTo(*data,Extended(kTRUE),SumW2Error(kTRUE),Save(),Range("1,2,3,4,5,etc."));
    else                FitResults = fMod.fitTo(*data,Extended(kTRUE),SumW2Error(kTRUE),Save(),Range("Full"));

What I see is an increase in the order of 100 fold, it is puzzling to me that such a huge increase could be due to integrals computing.