I think TB and IM spaces have more of an effect on our FWD V6 Nissan motors than most others because of the shitty IM’s we get. It’s like they made the motor for the 300ZX (your case) or the 350Z (my case) with the RWD engine bay clearance, then decided they would rotate the motor 90* and squeeze it into our engine bays and throw a pathetic little manifold on top :banghead :lol I know upper and lower plenum spacers on my car are good for a solid 10whp/10wtq.