Like i say its dependent on the car. If Kanga has a 159 then thats a newer car so i'd imagine the exhaust to be more restrictive than the 156. The only way you'll know for sure is to RR it before and after but like you say thats an expense you could do without.
Exhausts are an absolute minefield on N/A engines and whats good for one car may not be for the next. Unless you're gonna spend big bucks on a pulse tuned gas scavenging all singing all dancing affair then the result is going to be hard to determine until you've got it done!
Good luck anyway
Sam