Tuning GT 86 engine n/a

Hi does any know off any firm who has tuned a FA 20 N/A engine with out turbo or super charging but with cams throttle body's etc

not really. in 99% situations it doesn't make sense to go NA for power, so it will be easier to do it yourself than find someone to do it.
change out the exhaust header, improve intake, individual throttle bodies are waste of time and pain in the ass for the boxer engine, take the heads to professionals to do some head work, change out all valvetrain for better components to raise rev limit a bit. it is a long way. and every additional hp will be more expensive.
lose weight first :)