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Wheel repair upsets balance?

Hey all, 

My M3 and I recently had a "lawn-mowing off-track excursion" in the rain 
at Summit Point Raceway. Now, the front two alloy wheels got slightly 
scratched up by some rocks lodged in the mud, and looked repairable. But 
the dealer told me he had told the insurance company he wanted to order 
two _new_ (!!) BMW Motorsport wheels to replace the old ones. I found 
this rather odd, since wheel repair isn't too expensive. When I asked him 
why, he told me that the the process to repair a wheel involves melting 
and molding the alloy, which throws off the balance of the wheel. He said 
that I wouldn't feel the "mis-balance" driving 90mph, but I'd definately
feel it going 120mph+.

A few weeks back, I "curbed" my right rear wheel on one of those nice one 
foot high concrete curbs. Well, I got the wheel repaired and put it back 
on. The guy who did the repair just put the wheel back on with an impact 
wrench (in the proper pattern, mind you) but didn't torque the lugnuts.
Well, after I got the wheel back on, I continued on with my autocrossing 
activities. Everything was fine, but when the car goes through quick hard 
left hand turns, I _barely_ feel the right rear wheel just kinda 
shake/shimmy/vibrate a few times before it settles back down. It's _very_ 
faint, it almost feels as if I've run over the edge of a cone. This 
_always_ happens on quick hard left hand turns at the autocross. It 
doesn't happen in day-to-day driving, it doesn't happen in long left 
hand sweepers, it doesn't happen at 120mph on the main straight of Summit 
Point (like the dealer said it would), and it doesn't happen on fast 
left hand turns at 70mph or so either. I originally thought that since 
the lugnuts hadn't been properly torqued (I didn't have a torque wrench 
at the time, and didn't it was all that important), they might have been 
a bit loose, and the quick load shift from all four wheels to the right 
rear wheel may have caused the wheel to shake a little before the load 
shifted back to normal. Or maybe the guy who fixed the wheel didn't 
properly put the tire back on the wheel (is that even possible?) But
after speaking with the dealer, I thought maybe it was because the wheel
had been repaired. So the question is, anyone have any idea what's causing
this problem? If it's because the wheel has been repaired, should I have
someone balance all four wheels? Will this fix it? Or should I just give
up on the repaired wheel and swap my full-sized spare wheel on?

Thanks in advance for any help any of you guys can offer me...
My copy of the Roundel just got here, and it looks like an interesting 
issue. Am I the only one that puts aside everything I need to do to make 
time for reading the Roundel when it gets here? I guess I'll have to 
browse through and look at all the new performance parts that came out 
for the E36 M3 and drool over them while I wait for my car to get out of 
the shop... argh.

Dave
'91 Pontiac Grand Prix SE (automatic) for the next 2 weeks. sigh.