I recently tried a combination of selegiline and amphetamine because I don't have much regard for my health anymore: it actually kept my blood pressure and heart rate LOW. In fact it reduced both to a point above which I usually find myself even when I'm not on anything at all. I can't say whether it reduces the recreational effects, since I don't get any from amphetamines for the most part (as I have mentioned a dozen or so times by now). Makes sense, I guess, since D1 receptors, when activated, lower blood pressure and heart rate and have a mildly soporific effect; the selegiline just shifts the balance in favour of dopamine, where when taken alone, dexamph is preponderantly noradrenergic.
Like you, my BP and heart rate are permanently high (possibly as a result of amphetamine use). When I first tried dexamph (about 2 months ago) I could go fairly high without any noticeable sympathomimetic effects, but now I can't take even a single milligram without feeling as if I were about to have a heart attack or stroke.
It's really striking how capricious dexamph is in its effects on my mind: one - and only one - time it made me feel vaguely euphoric; usually it makes me very dysphoric; another time - and again only one time - it made me rather horny; mostly it reduces my libido; sometimes it doesn't do anything to my heart rate or blood pressure; other times it increases them to dangerous levels; a few times it has enhanced my intellectual powers; usually it turns me into an even bigger dumbass than I already am. (I don't mix it with anything, by the way.)