Mr Bateson,
The filtration that a pair of tights will give vs a properly produced cone or panel is negligible - the particles that cause engine wear will not be troubled by the mesh in tights. On that basis I don't recommend it.
The amount of power an engine will produce is proportional to the air pressure and density. I'm sure you know the cold air-higher density bit, so I won't repeat that.
The bit most people don't consider is the pressure drop across the filter media. The pressure entering the engine should be as close as is possible to atmospheric, as this is your high pressure reservoir (and assuming no mechanical pressure charging) so you want as much of it driving into the low pressure areas of the manifold. The best way to do this is to have a high surface area filter as air will always flow to the path of least resistance. This means that when the media is caked it's resistance will increase so flow will be taken in though low resistance uncaked areas.
The bottom line to that is that if you have a big filter you have more chance of flowing via lower resistance areas, and that translates to less pressure loss and higher manifold pressures, which of course translate to higher cylinder pressures.
If you consider engines on competition vehicles you will see they are always as large as can be packaged into the body, sometimes to the extent of looking ridiculous in the cases of arena racing monster trucks.
A pipe of similar diameter to the throttle body covered with enough tights layers to effect good filtration is not the best solution to this due to a single flat surface being prone to blockage.
Ultimately the rules of good inlet design, pre-dynamic regions, are;
Intake is placed out of any dust streams.
Intake fed from a high pressure area on the bodywork.
Forward facing intake is usually desirable, to try to stagnate flow, but don't mistake this for ram-air. That's different, and in most cases wishful thinking at road speeds.
Intake fed from cool ambient air.
Large filter media surface area.
Smooth duct transitions from filter media towards throttle/dynamic areas.
Follow that and you'll be doing the best you can.
If you want an actual opinion, and a practical one, i'd say use as big a cone type filter as you can fit and enclose it in a large cylinder so it can be evenly fed from all sides to avoid preferential caking.
On the exhaust baffle question, yes and yes. However the length of the MGF/TF system prior to the cat and cat position means that the major reflection wave will be done from the cat matrix and not the baffles in the backbox. From previous professional experience and by inspection of the backbox the baffles are sound reduction and not major reflection planes (even if they were the wave would be damped in the cat matrix).
From my own personal experience (
http://forums.mg-rover.org/showthread.php?t=381340 ) it sounds nicer and runs better with them out, although there was also more exhaust work done around it.
