Looking at my EGR tube I see the pervious owner, instead of purchasing a new one, seems to have welded patches over the cracks. Is this ok, or should I replace the whole tube?

That EGR tube is awful thin. I had mind welded back to the flange when it broke. Actual repairs to the tube itself, because it is thin, may not be reliable. If the patches are not stainless steel, eventually it will fail. If the tube leaks - that is bad.

I've always thought that a inexpensive repair would be to using the flanges from the factory tube, and use a piece of stainless steel flex in place of rigid tube.

You can also cut the damaged portion of the ribbed flex tubing away and replace it with high temperature hose. You can get it from a muffler shop or NAPA. 3/4 inch is the correct size. I used it successfully to take up the difference left after a mis-calculation while building a crossover pipe for my turbo. It's often used to connect the air tube to the catalytic converter on cars that have it. The tubing is green.

I wouldn't "weld" it. You could braze it with some sheet stainless steel and contact SRA (Stan Rubenstine & Associates) they carry a brazing paste for stanless that runs about $4 per oz.(you only need one ounce)

Banzai !!!!!!!!!

I have sucessfully brazed the tube with plain brazing rod. I doubt that you would be able to weld the material.

I've also used J&B Weld Quick-Set to fill a crack on the EGR end where the flange and tube connect. Been working for over a year, now.

You can also purchase a new one from the Fiero Store or FOCOA, and maybe Rodney.