Buying tuned s/h air rifle only to 'fix it' by putting back in factory parts

[look no hands]

I'd only buy a tuned gun if it was a Venom Conversions, Venom Arms Company tune or V-Mach tune, even then I'd need documented evidence, otherwise its new only for me.

I obtained a supposedly Venom tuned rifle once, to only find out that it was packed full of grease and had a broken spring, the internals where completely standard as well, obviously I wilI never deal with that person again, have a couple of home tuned rifles I bought and both are pretty nice to shoot, one was at the last Bash and for a home tune is pretty good, no twang and feels like a tack driver.

Pete