@redtarga - I reckon you've hit the nail on the head. I just went out to the car and looking at the wheels, I was wrong about the wheels and now think there is no method of centring the wheel on the hub, bar the studs.  So I reckon this may be the cause of many intermittent and varying shakes. So before I do anything else, it's time to change the wheels. (Drawdown on the mortgage time).
 
 @Phiz - do the R32 wheels fit the lip on the hub snuggly ?  (Is there a lip on the hub, like my Camry?)
I need to check with 18yr old to see if he likes the look. I don't care as much about the look. 
Maybe I should check a Wheel thread on the forum.....
 
thanks for all the help, a relatively major breakthrough.... disc milling etc can wait and may not be requred.... 

The problem with aftermarket wheels for MR2's is not stud pattern but the need to find a staggered set.
 
The Nissan GTST and GTR 16" have large tapered centers and neither will fit the Toyota hub spiggot, so something needs to be done about that. Someone else on here may know if metal hub rings are available.
 
Apart from centering, the offset/width on the front is important if you want good shake free steering with no tramlining.
The GTST wheels have a 40mm offset that is close to stock (45), so the scrub radius is not changed much, and at 6.5" they are not much wider than stock (6")
 
Also apart from looks, with 16's you need to think about tyre availability.
The fronts are no problem, but the rear choice is limited in a 225/45R16 if you want to retain the stock rolling diameter.
FYI, if you were to use a 225/50R16 on the GTR rear (larger rolling diameter than OEM) with a lowered suspension it will probably rub on bumps, so guard rolling needed.
 
EDIT
I just found a pic of the Nissan GTST/GTR combo  to give you an idea of what they look like. The car has been lowered about 1.5"
 
 
 
 

 Sure enough, I took a wheel off and it's ID is 70.x mm with no ring.
 I look up eBay for hub centric rings for the 60.1mm hub spigot and wouldn't you know it...there are 2 sizes that might be correct ..OD=70.1mm or 70.5mm !! My ruler and eyecrometer lacks the precision to tell which one I need.
 The wheel is an ROH 17"x 8" with an offset of approx. 32mm (measured lying on the garage floor with tyre on).
 I'm hoping someone here might know, even a likeliness of which one is the one to get.
 I will try to contact ROH and ask also.
 Anyway this is a significant diagnosis, I'm confident that there is also some disc runout to fix also but at least the
freeway shakes will be gone. I hope I haven't stressed the studs too much.
Maybe I should post this in a wheel thread ??

 I need to replace the bushes in the rear control arms, 1990 SW20 3SGTE.
 In the parts catalogs they are not shown so it appears I have to buy the whole control arm.
 Buying a whole kit seems overkill as well, unless there are other members looking to replace 1 or 2 different bushes ?
 Any suggestions?  Thanks...

Bushes in rear control arms ??  Do you mean the transverse control arms between the ball joint and the chassis?
Or the transverse toe in adjustment links bushes and if these which end? Chassis or hub?
Where are you located. I may have these bits available.

TwoDogs
 I need to replace the bushes in the rear control arms, 1990 SW20 3SGTE.
 In the parts catalogs they are not shown so it appears I have to buy the whole control arm.
 Buying a whole kit seems overkill as well, unless there are other members looking to replace 1 or 2 different bushes ?
 Any suggestions?  Thanks...

You can buy the whole poly bush kit out of the USA for about $150. The trick is getting your hands on a press to push out the old ones. Whole job will take about a day. It's a must for any MR2.

Thanks B24,
 took your advice and should have them in a couple of weeks .
 cheers

@Falcon,
 
 I only just saw your response... might have been a solution but too late now, I have bought the "complete set".
Thanks anyway...