stalling at high rpms and low rpms? rough idle. couple codes.

[dumpstafresh]

My buddies svx (my old svx) started stalling at idle and with slow acceleration a couple weeks ago.

his codes were:
Maf sensor
O2's 1+2
Egr system (code 56)
and knock sensor(witch is intermitant cause of a bad wire somewhere)
(also the Crank pos. sensor code has poped up a couple times in the past. not lately though.)

So he replaced the spark plugs, fuel filter, o2's and cleaned the maf.

It didnt realy help much. the idle is a little smoother.
it seems like it runs fine untill its warm. if he gets on it, it will usually die around 5000 or so rpms.
It doesnt realy seem like a misfire because all power gets cut off.
it will also die randomly while idling or barely accelerating. sometimes being hard to start and keep running again.

The maf code keeps coming back and the egr will show up(not every time the car dies though).

Any ideas as to what could be the problem would be much appreciated. before he starts throwing new parts on it. since a maf is $300 and a crank sensor is 180 or something.

sorry about the long post. i just like to be as detailed as possible, for future searchers like myself.