I hyave an 86 SE with a F308 rebody and recently norticed a fairly strong vibration in the steering wheel around 67-70 mph. The tires were just changed/balanced today but the vibration level has not improved much. Does anyone have thoughts on probable causes for this problem? Tie rods strike me as a potential problem area for the vibration but my suspension experience is very limited on Fieros and I could use some diagnostic suggestions.

Does the vibration feel like a 'hum' or does the vibration make the steering wheel swing left/right and change oscillation speed with car speed?

Do you have wheel spacers that are not hub-centric (ie are the wheels centered on the spacers by the tapered nature of the lug nuts or by a metal collar on your spacers)? If so, then you can't be guaranteed that the lugs nuts will center the rim on the hub perfectly. You can balance the tires all you want but if they're not centered on the spindles they'll vibrate.

If no spacers, then a a worn tie rod or two is a possibility - to check, raise the front of the car and grab the tire at the 3 and 9 o'clock position with the steering wheel locked and wiggle the tire. If there's any play in that axis, then either your inner or outter tie rod ends are worn. To tell which one it is, have someone wiggle the tire while you look at either end of the tie rod to see where the relative movement is happening. There won't be much, but there should be none. It's straight forward if the outer tie rod end is worn, but a little more complicated if the inner one is moving. The inner tie rod is covered by the rack boot. If it appears as though the inner one is moving, you have to note whether the movement is in and out, or up and down. If it's in and out, then the inner tie rod is worn. If it's up and down, but only on the passenger side, then it's the steering rack bushing at the end of the steering rack tube that is worn out.

If you see no movement on the tie rods, then grab the wheels at the 12 and 6 o'clock positions and wiggle them. If you get movement, then either your upper or lower ball joints are worn. Again, just look closely at each of them while someone else wiggles the wheel and look for relative movement between the knuckle and the control arm.

the 3 common causes after out of balance tire:
Ball joint
bad steering rack bushing
bad shock

the easy answer for diagnosis is to go get an alignment - and then - they will refuse to do it because ____ is worn, and needs replacement
then ya know

It might be a wheel bearing. I kinda doubt it but possible. Cheap and quick fix.

Yeah we still haven't heard if this is an slower occilating steering wheel type vibration the type typically caused by a wheel out of balance, or a buzz or grind type caused by brakes, or bearings, or tires, or road noise, or loose components.