Maybe I am the one missing the boat here but what I thought the OP said was he got flavors that somewhat remind him of diacetyl. I have found I can get this in beers with MO. Often times it is very pleasant but that it can sometimes conflict with other floavors in the beer.
For me, I found that the MO in conjunction with the other malts and hops I was using in my IPA had a "sharp" character that reminded me of diacetyl. It was in the back ground, not in your face. Still made a very drinkable beer. Cutting back on the MO made a beer that had a better balance of flavors. Cutting it out completely left a more one dimensional malt character.
In addition to all that, I am toying around with a "single hop, single malt" IPA (All Columbus, All MO with the hops changing from batch to batch) and I found that cutting back on the "single malt" to about 80% made a better tasting beer (to me)..
I guess the thing I should point out is I am making American IPAs, not English. For English those types of biscuity and buttery flavors are essential but they can conflict with American styles.
I also think that back on all the times I thought that English yeasts threw so much diacetyl (and a lot of strains do) but now I believe mroe of that character may have come from the malt.