Universal sports cats

[lolsteve]

So recently purchased a new janspeed manifold + decat pipe for £100, bargain since the manifold alone is ~£250 new.
Problem is the decat, while it'll obviously fail an mot it apparently looses power on the vvc engines which has been backed up by dyno results

The plan is to weld in a universal sports cat like that found on ebay
http://www.ebay.co.uk/itm/161104947289?s...1423.l2649

Does anyone know much about them or used them though? Before I buy one and find out it's no better than the standard cat