maybe a 90 degree on the front and a wrap to center on the back, then use a 1" tube to line it all up...

engine...
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your tuned pipes...

this would be kinda like an "H" pipe like they use on v8's... just a thought...
the only real work involved would be the "H" pipe construction, u need someone with a laser welder...

you also might be able to get away with two elbows and two t-pipes....


eblow in from 90 front cylinder, then t-pipe for exhaust, then t-pipe from wrap to center "rear cylinder" then another elbow to the secound tuned pipe.

this would be the same design but the elbows would decrease the turbulance a bit...