Yeah the part about the fat bottom end being required is true in some cases, espesially with high powered modified engines. It may well be the case with your S7 and you are being hindered from running the lsn rich by the MC9 plug....thats a bit of a cold choice for 20% Nitro. I think you should get a RB#6 plug and try a tune with that, and also if you have not already got, get a 13th CB

Is your bottom end crisp and responsive ?...or do you just want more punch ?

TM