Volvo: 1998 V70 AWD HELP!, mass air flow, passat diesel

Question
Hello:
My mechanic and I have been unable to diagnose a problem I have been having with my wagon.  The diagnostic code says that I have a faulty Mass Air Flow unit. Code FET121 MAF.  We installed a new one and the car continues to fall on it's face and/or out right stall at excelleration from stop, going 60mph, idalling at a stop and any other odd time.  The same diagnostic code keeps appearing.  We did a smoke test on the engine and found a leak in a connection near the turbo.  We fixed that and I am still having the problem.  They other day it fell on it's face but it didn't stall but there was no power moving the car forward although when I gave it gas the RPM did rise to about 2500 but not as much as it would be if I was reving the engine normally.  At this point I'm about to give up and look for a new car.  I wish I had heeded all the warnings about getting the 1998 V70 AWD turbo wagon, but I couldn't resist the turbo AWD.
 
If I can not fix this problem I'm looking into 2003-2004 Mini's, BMW 325xiT, The smaller Volvo wagon...can't remeber the model..it has the Taurus frame which I'm not so excited about, Audie A4 Wagon, SAAB wagon? not sure how they are these days, or something diesel.  I would love a Passat diesel wagon but they are pricey still.

Can you give me any suggestions on these choices?

Answer
Wenonah,
MAF's have been troubesome in that vehicle. Is it a good MAF I have seen bad ones out of the box. Secondly monitor the O2 sensors and see that they are working properly. I have had many a difficult time with O2 sensors. If you need new ones get ONLY the direct replacement up-dated ones from Volvo. Check all the intercooler hoses if you have not already done that. A leaking hose will cause a lack of power and set some codes. I have seen two cars that have had parking block mishaps with the intercooler cracking the bottom tank.