There are 2 different 3.0l 200 efi's. Is yours the standard fishing motor or is it the work 3L. The work 3L has lower compression than the fishing 200/225/250 which use the same heads as the part/casting number is the same. 300x heads would give you more compression. It is almost impossible to find used 300x heads. Call Eric Simon his heads are cheaper than buying stock merc heads and they have the cool factor being cnc machined and anodized! Who did your computer was it Eric because to my knowledge he is the only one in the US with the capabilities. You could also add a light flywheel, popit diverter, and hydro tech tuner and make 300hp.