Typically, if you are bumping up the bore size while using the same head (1.6L), it will only help. It will make it flow better #s because there is more room in the combustion chamber to let the air flow out the valves. If you look at head flow charts, heads always flow better with a bigger bore and/or using a bigger flow tube on the exhaust side. Being a DI engine, I would prefer to see a custom piston made so that you can get the valve reliefs in the correct spot and the correct shape/location for where the injector squirts.Over all, the MR18 bottom end is just as strong as the MR16, until you make big power, then the wrist pin becomes an issue. This is easily fixed with just using an aftermarket piston and rod with a bigger pin, obviously. But, the only reason i don't think its worth even going that far in is because of the cylinder head. You would need to do a custom cam grind for sure to make it worth while, then have to deal with the lack of duel cam phasing to bring on boost faster and make more low end with the turbo. We did check to see if we could use a MR16 head, and while it will bolt up and probably work, your then stuck with a wrong sized valve area, so I am not sure how that would effect things. We have already asked our machine shop to get us that information. If we end up finding that we can get away with a MR16 head using the MR18 block, then we could easily make an MR20DDT hybrid engine.