There are suggestions on recent facebook posts that the air filter nose located on the drivers side wing restricts air flow into the engine when at speed.
If my calculations are correct then a 4.6 litre 4 stroke engine will suck in 4.6 litres of air every 2 revs. So at say 5000rpm means the engine is taking in nearly 200 litres of air per second!! ……… going through that flat shaped tip of the air filter. That seems a lot of air.
So there may be a good case to make the mod ….. those who have done it say they can tell the difference. Some reckon another 5bhp to be gained.
MG ZT info mods and maintenance 