rx7learner

I got an S4 with no shaft play at all that sat on a shelf for many years pulled off a TII that blew a coolant seal at 70K.

I pulled the turbo apart and cleaned it very well with carb cleaner and ported the wastegate and welded an SS washer onto the stock wastegate cover.

I put it back together, installed it, and got a bunch of oil down the downpipe causing a bunch of smoke.

I dont know anything about rebuilding a turbo but considering there's no shaftplay and the turbo was pulled fairly early in its life... when I pulled it apart again after the oil leak incident I realized that some of the bolts that go though those hold down plates were fairly loose and I'm not sure that I put them back in the same place I took them off. It looks like there is a silver cap under the exhaust impeller that is compressed when these bolts are tightened. Could my improper reinstall have been the cause my oil issue?

Please advise. Thanks in advance.