I bought I nice new siamese for £107, but the little pipe had the wrong profile for the exhaust port in the head, wasn't long enough where it went into the head, AND was slightly too narrow meaning it was a loose fit both in the head and where it clamps up to the other pipe.
I needed to use it, so did, and therefore couldn't return it, but the little pipe keeps working loose and it was driving me mad. So, I made up a loop, braised it to the inside of the pipe, made up a little aluminium spacer to fit in a hole in the head (didn't want to damage the head) and then made a spring to hold it all together!
So, got a cheap pipe and saved a few quid, but spent about 3 hours continually refitting the loose pipe, then several hours working out a solution, making the spring and ally spacer, braising the loop, fitting and testing it (it works!)...
That was one bargain!