My daughter's 95 940 Turbo has a bad stumble/surge problem. It went away after 200 mile highway trip, but now over five days has become gradually worse again. Any kind of load and it starts bucking. I have to give extremely light pedal pressure to get up to speed.

I have:
replaced fuel filter
filled up tank with gas
put in big bottle of Techron
replaced fuel pump relay
re-soldered FI relay
swapped out FPR
Swapped out AMM
replaced small vacuum hoses that looked crumbly
inspected big turbo hoses
swapped coil

Before I build the tool to pressurize the turbo hoses as described in the FAQ or buy a fuel pressure tester, is there a way of determining if there is a air system leak vs low fuel pressure? That is, if there is a air pressure or vacuum leak will it be running rich, so that I could check the plugs for fouling, the exhaust pipe for soot, and the exhust for black smoke? If it shows these symptoms, should I build the tool to look for air sytem leaks? If not, then buy the fuel system tester?

This looks a little weird but you can try looking for leaks by duct taping the family vacuum cleaner to the exhaust pipe. Light an insense stick and move it around the engine. Any leaks will quickly suck in the smoke. What scent to use is up to you. All types seem to work equally well.........

Thanks for idea. I am ready to try anything at this point.

Since there was no black smoke at exhaust or plugs fouled, I went out and bought a fuel pressure tester. The pressure checks out, at least at idle.

So I'll ask the wife where the incense went to and give it a try.