Honestly, aside from the B21F plenum intake/wouldn't bother, especially if keeping it stock/K-jet.
The exhaust housing/stock exhaust/intercooler/wastegate housing/pre-90 pancake/log exhaust manifold/cylinder head/k-jet plate restrict things worse and make for worse efficiency/economy/longevity issues.
Won't really help fuel econ or longevity, the pancake manifold does suck for flow, but other things are worse and it makes the car less orginal/more hacking and maiming, would not convert. The accordion hose sucks, but D088 repops it or heavy duty wire-reinforced high temp fuel hose for truck/heavy equip and military applications works, or bubble flex couplings & hard pipe with metal end tank D088 intercooler/similar?
Maybe with an auto trans/3rd engine mount & eliminate the leaky/brittle plastic tank IC that is so woeful/deficient/defective on these cars before hard/super rigid piping it though?
The flex in the system is there for a reason?
That said, if you do manage to solve/upgrade all that, but still keep it SOHC, the B21F plenum intake is worth ~+40ftlbs on the fairly mild SOHC motor of the best of the stock casting intakes if you don't lose your mind drinking the redblock timebomb k@@l-@id (Rodney dangerfield impression genie alladdin eyes?) & go 16V or Nathaninwa intake?
There are less $ per HP more powerful engines that fit in the 240 bay at that point...
Highest stock performing metal corvette intakes for the ellis-juans & the really pretty EFI intake (very similar to the 'vette intake, just V6) for B280 are pretty?
For broad powerband, cast, single throttle body/low dollar high volume warranty/lemon law compliant mass production pieces, anyway.
It's sorta like the E-fan conversion on a 240T;
You can do it/it's easy enough to hack in there for low dollars initially (quintessentially TB)/gives you something do mess with if you're bored or /.17?/hr / first tweak hit's cheap/free.
Might not hurt per se, but not amazing.
