Actually it's not smaller Steve. The td uses 11-blade wheel, ours is a 6+6, they are the same size But 6+6 is more efficient in the td04 compressor housing. We have tried the 11 blade wheel before too. If using with stock td04 turbine side, it will surge with anything over 1.5bar. If you had compared the turbine side you would have noticed that our stage 2 turbine wheel Is much bigger than than the stock turbine wheel on the td-unit. What you have now will spool faster and make less power. Our stage 2 is lagier, but capable of 1.8bar efficiently and more power overall. see below... here's our old 11-blade billet Vs. 6+6 cast wheel (our stage 2 has billet version of this same wheel) .... 11-blade looks bigger visually right? take the housings off and break out the vernier calipers and guess what...they are the same size... Not taking a dig at Td's turbos...its a solid combo/product..but its limited to 1.5bar and 300~bhp roughly. Our's is made for 320-330bhp...but all that extra horsepower comes at the expense of extra lag. for road, i think you will be happier with what you have one now mate.