I've tried a few of these lovely cheap induction mods now, primarily because of my poor DIY skills, and curiosity. I thought I'd give an opinion on a few of the different cheapie options, I've personally tried.
The original Cooperman mod has been used loads here it seems, and it does sound good. Shame my poor DIY skills caused it to fall off. I'm blaming the short legs I got on my silicone bend.
No induction pipe, found out this one when my "cooperman" fell off. It definitely sounds best. Although I felt you lost/moved(?) too much power/torque. But to be fair the sound is almost worth it. Best sound of the bunch, by a long shot!
The little rubber Fiat 1.1/1.2 (from memory) induction pipe. The easiest to fit and sounds better than the standard pipe. I got a new genuine fiat one, for a little less than £10 delivered from eBay.
The flexi-pipe method is the second easiest to fit, only cutting the wire could cause any issues, it's that simple! But unless you can buy a tiny bit, you'll end up with enough pipe for half a dozen cars.
I've tried another one now, the most recently fitted flexi-pipe was lacking in the sound department an I'd recently had a Marelli exhaust fitted. So I found ebay item number 190886048846, for about £15. It was, to my eye, a good bend and from a little reading I've done I was convinced it had a chance of sounding ok. An apart from a 10cm silicone joining hose, and a couple of clips (left over from previous goes) it was ordered an fitted. I'll try to add a couple of photos, of my new set up. But a quick Italian tune up says induction mod fitting days are over.