Hello mate
!
I have seen the one you mean on ebay (it has a polished alloy intake pipe and a cone filter?)
The kit itself looks to be quite good value for money for what you get - the elbow into the TB, the alloy pipe with breather hose take off and, of course, the filter itself (although I can't comment on the quality of the filtration material used as I've not seen it in the flesh but it looks like a cotton one similar to K&N and GREEN.)
On the power gains it claims, there is
no way it will give 5-10 bhp on a Seicento engine. That would be about a 15% gain over standard and to expect any kind of 'bolt on' engine tuning part to give a 15% increase on its own is stretching it a bit!
I've been modifying my cars for 15 years and have designed and built a number of induction systems on various different cars and there are 2 elements to a good induction system - 1) increasing the flow and volume of air. and 2) keeping it as cold as posible.
This ebay kit only performs the first function - it has no cold air supply and is an 'open' system which will draw in hot air from the engine bay (and let's be honest Cinq / Sei engines are not the coolest running due to the size of the bay etc..) Simply increasing the flow rate and not reducing the temperature of the intake air can negate any horsepower gains you might have made.
My advice would be to either look at a 'sealed' induction system (all the top-of-the-range systems from Pipercross, Quikshift, BMC, K&N etc.. all used some kind of 'sealed' system but are expensive).
The alternative would be to get the ebay system but think about a way of, at the very least, ducting some cold air to the filter and placing some sort of shield between it and sources of high heat like the exhaust manifold.
If you have a look at my gallery page you will see the 'Quikshift Racing' system I have is
entirely sealed from the engine bay and has a large intake duct taking up the whole of the passenger side grill which collects the air hitting the front of the car and forces it directly into the airbox under pressure creating a 'ram' effect.
(I was thinking about doing a guide on induction systems for the forum in the future so I won't go into any more detail now).
The performance gains I have with my set up are amazing.
Sorry for the long reply, but to sum up - on the face of it, the value for money aspect looks good but the system in 'incomplete'.
Hope some of this helped.