Horrible noise from wastegate area.....

["Pearce,MR,NAIC4,PEARCEM3 M" <PEARCEM3@BTLIP04.BT.CO.UK>]

Fellow listers,

I think I need to draw on your collective wisdom, with respect to a
harsh, metallic noise coming from the turbo/wastegate area on my 1984
Ur-q. The symptoms are as follows...

Under normal driving conditions, everything is as it should be, engine
pulls to red line, no smoke, no misfire. Under *hard* acceleration,
mainly in second gear, less in first and third, a *loud* ZINGGGGGGG
sound emanates from around the wastegate area, co-incidentally at full
boost. Backing off the throttle stops the noise. I don't get this noise
at full boost in fourth or fifth. The noise is constant in frequency,
I'd guess at between 100-200 Hz. ish. The noise does not affect the
car's performance, other than making me back off through mechanical
sympathy...

Everything seems screwed together. Possible thoughts...

Turbo blades on casing due to excess spindle play at full boost, but no
swarf in I/C pipe.
Wastegate somehow faulty... maybe diaphragm related?
Soggy engine mounts causing some problem (hence mainly in lower gears,
engine flexes less in higher gears?)

Anyone heard anything like this before???

Yours perplexedly,

Malc Pearce.