Both the stock systems on the Renault and TC/S Europas actually work very well. The only improvement would be to fit aftermarket bell mouths to a Stromberg equipped TC/S. That said there are two issues with the stock systems: dirt and high air temps.
Road dirt and dust seems to be the most concentrated right where both systems suck in their "fresh" air. Period tests commented on the fact that the Renault air filter became restrictive fairly quickly. I run a twin Dell equipped crossflow with a TC/S air box and filter. I find that I have ti change the air filter every 2K to 3K kilometres or performance suffers.
Equally spooky is the Lotus engineers unerring ability to find the hottest possible intake air. Intake air temps can get up to 120°F+! Building an air box and accessing air down low towards the front can make a huge difference.
My plan is to fit an air filter from a Jag XJ6 series 3 and duct it to cold air just behind the driver's seat. That will draw cool air and the larger filter area will last much much longer.
What should Mr. A. Spares do? Fit an airbox and a remote filter down low on the driver's side. Here are some air boxes for single Webers:
http://www.bitsofitaly.com/cold-air-box-intake(The MGB set up would be perfect)
https://www.efihardware.com/products/c59/Air-Boxes(you have to cut out the base plate to suit)
When choosing a filter bear in mind that more surface area (lots of pleats) is better than bigger holes (more dirt along with the more air).
