I recently installed rebuilt head's on my EA82 in a Trike.  Used new lifters.  Started engine, ran perfect, but after reving engine @ about 2,500 RPM for 10 seconds,  returning to idle, it run rough and I could hear hissing out of the exhaust (short dual glasspacks). driving it for a couple miles and it would idle fine, hissing gone. this would happen every time after engine cooled down.  I pulled towers back off,   installed old HLA's that worked fine befor headjob,  put on timing belts and no compression.(I know you knew that).  Pulled tower's again,  bled down lifters and compression was good again,  but still it start's and idles fine,  just leak's out exhaust valves for a couple minutes after reving it up for a while.  The head's had new seat's and guides and resurfaced,  but the valves were reground.  At first I thought the HLA's were pumping up or something, that's the reason I changed them out. I checked bypass valves in the towers and they were fine. Only thing I can guess, a couple of the valves were warped,  grinding straightened them out,  and they go back warped after a while, then straighten up.  Yes,  I poured solvent in the exhaust ports and not a drop of it leaked past the valves. A compression test was fine, I'm thinking about replacing the exhaust valves next.  lucky  the motor is very easy to work on out in the open on a trike.  If this had been in a car,  I would ov had a door kicked in by now.

Edited August 20, 20178 yr by montermahan

I think my reply to this got lost in cyberspace. Save my breath in long story and my experience...try new valve springs. I had very similar followed similar every path possible then ignored advice of d1ck brains that welded the cracks ....new valve springs from Subaru Japan and all was fixed and better. Bet me left but on your problem