How can i tell if a wastegate is still good?
Im about to purchase a Tial wastegate for a good price.

 

You can unbolt the gate to check the diaphram when you've received it, if you dare, or simply test it. No other way to do it.

 

haha what do you mean if you dare?

 

You'd be surprised how many people can get the bolts off and not be able to put it back together without pinching & tearing the diaphram

 

any tips to putting it back?

 

be very very careful, lol. ive never done it but i have done one of those AEM FPRs that has a similar diaphragm but smaller, and even that was a little tricky to do without pinching it. What i did do tho was use a feeler gauge to hold the diaphragm in place while i tightened the bolts down just tight enough where i could still pull the feeler gauge out. by that time the bottom and top are so close together the diaphragm can move. haven't had a problem since. so i guess you could try something similar with the wastegate.