These are what I've tried so far in my .22 MRod: JSB Heavies, JSB 15.9gr, Baracuda Match, Crosman Premiers Box, Crosman Pointed, Predators, RWS Meister, RWS Superdomes, and Beeman FTS. So far the best groups I get are with the Beeman FTS and the Predators. Your MRod may not like the Beeman FTS, but if you're asking for my opinion, then I would recommend the Beeman FTS, since it works best in mine. I have some H&N FTT, H&N Rabbit Magnum II, and some CPHP on the way to test out.
Some info on my MRod: it's stock; nothing has been done to it, other than adjusting it to 2900 psi. I still get the occasional flier, but that hasn't deter me from shooting it. My two farthest kills so far are two pigeons at 94 yards, measured with a Nikon Prostaff 550 rangefinder.
Happy shooting!