1/8 inch N.P.T. brass socket head plugs work well and cost next to nothing.

The thread pitch and diameter is very nearly the same, the brass being soft enough to conform and with enough interference in combination with the nature of pipe threading that they fit tightly and don't fall out.

Just an alternative.

My heat exchangers came off surprisingly easy. Then again, my exchangers weren't all that rusty either. I soaked the nuts with WD40 for about 5 days. I was going to use a MAPP torch but the nuts backed off with out a fight. They must have been off previously. Two exhaust studs backed out. I am replacing those. I got my exchangers sandblasted and cleaned up last night. Tonight is the paint and oven baked heat exchangers. Good times. I haven't tried removing the air injectors yet. They don't appear to be too hard to remove. I'm still waiting on my parts.

I got the ones with allen heads from EBS Racing (www.ebsracing.com).

Here is a previous thread talking about them.
http://forums.pelicanparts.com/911-engine-rebuilding-forum/107347-air-injector-plug-size.html

http://forums.pelicanparts.com/uploa...ectionPlug.jpg