The extra groove and ring shouldn't have a detrimental affect on compression, however the v shaped chamber in the piston crown will. The extra ring may increase piston wear though as it will clean some oil off the bore which a diesel would normally partially replace with the lubricity of the fuel.
Compression wise, the difference in power may not be enough to notice though unless you are in an out and out drag with another series 2.25P :D:D.
Fuel consumption may increase.
If it runs, and you are happy with it then fine, it may last for another 200,000kms.

