Chevrolet Repair: 1997 s10, mass air flow sensor, mass air flow

Question
Hello i have a 1997 S10, 4.3 Vortec that i am having issues with.
The truck is lacking power during driving, it has a trend of only doing this in the afternoon times on my way home from work, when the outside air temp is warmer. this usually starts to happen about 20 too 25 mins after running time at reg engine temp. The problem is very noticable and will start to spit and sputter as if it were missing. I am still able to drive it but it will only run at low rpm's. i do not have an rpm guage on this model so i do not know the exact. i can tell you that i have the codes P0101  ( mass air flow sensor performance) and P0339 ( crankshaft Position Sensor A circuit intermittent) showing when i have the service engine light on. I have removed both of these sensors and cleaned, replaced and still have the problem. I have tested the MAF sensor wiring and did come up with a low Voltage reading. I have changed sparkplugs, wires, distributor Cap, Rotor, and fuel filter, still Know different. this problem is seriously getting at me, especially the part that it showing a significant differance of performance when the outside air temp is hotter. if you could help this would be greatly appreciated

Answer
HI JAMES,FIRST OFF YOU CAN NOT CLEAN THE MASS AIR FLOW,IF THERE IS A CODE FOR THIS I WOULD REPLACE IT,SAME WITH THE CRANK SENSOR. HOWEVER IF THE TIMING CHAIN HAS STRETCHED THIS CODE FOR CRANK SENSOR MAY COME BACK. BUT TRY THESE PARTS FIRST. AS LONG AS YOU HAVE A 5 VOLT REFERENCE FROM COMPUTER TO THE MAS AIR FLOW THE PCM IS OK....AS FAR AS THE POOR RUNNING WHEN HOT.TRY TO REMOVE  BOTH OXYGEN SENSORS AND DRIVE IT LIKE THIS WHEN THE PROBLEM IS THERE. WE HAVE SEEN MANY OVERHEATED CONVERTORS BLOCKING OFF EXH FLOW. IF YOU HAD A VACUUM GAUGE YOU COULD CK THIS BY CHECKING THE VACUUM AT IDLE AND THEN RAISE THE IDLE TO 2OOO RPMS,VACUUM SHOULD DROP SLIGHTLY AND COME BACK UP TO ALMOST IDLE READING. IF THE GAUGE KEEPS DROPPING THE EXH IS PLUGGED. IF NOT THIS,, GET YOURSELF A FUEL PRESS GAUGE WHEN THIS IS ACTING UP AND CK THE PRESSURE,SHOULD BE AROUND 40 TO 45 LBS. THE OTHER PROBLEM I HAVE HAD WHEN THESE ENGS GET WARM IS THE COILS BREAK DOWN..I HOPE THIS HELPS YOU,,,TOM...