Picked this little fella up the other day ..1999 9C3 lumina.. spent today washing it , it has sat up for a while, it was a Salisbury ,N.C. police detective car only has 116k on the day, but the valve covers have been leaking for a while, and it had a hiccup sometimes when you would be driving, had a P0171 so today while it was raining I pulled it in the shop. changed the front valve cover gasket with one the the sorriest gaskets I have ever seen made (Came with the car) , removed the ECM connectors and reseated them, pulled the air box lid off to make sure their wasnt a rats nest in the filter, it was clean and new, and soon as i pulled the elbow off the tb , i seen the screen was damaged right where the air would be channeled into the maf, so i removed the screen , carefully and then checked the plugs and changed the oil, its had alot of parts thrown at it before being taken out of service, I think its a chinese tb no gm style part numbers on the tps unit or maf unit, 3 new coil packs, a new o2 sensor, plugs and plug wires, after putting it back together it drove fine going 1 mile home and then later after me and a buddy went to eat , I came home, cleared the codes and drove it about 10 miles , now it popped a Po103 right off the bat and took several attempts to start, but it did run better but still had a couple of hickups on the drive, so Im going to try and correct the damage to the screen and reinstall it. My fp tester should be here tomorrow also and ill check the pressure . I suspect either the pump or the chinese tb .

Cool!!

Overall looks like a clean car. New MAF time? Have you tried disconnecting the MAF and see what happens?

well since I took the screen out the po171 code has disappeared and doesn't show up as being even a pending code and I got the maf circuit a high-voltage code so today I'm going to put the screen back in after I tried to clear up the damaged area and I'm going to turn it around so that the damaged area is on the bottom of the throttle body so they clean straight air is getting to the map and I'm going to see how that works out if it'll ever stop ******* raining here I'm going to go to the junkyard and Robbie GM Factory MAF

Well still have problems, car was getting to the point it wouldn't start , so I disconnected it and it runs almost perfect other than some surging idle at stop lights, we going to the junkyard today and get a gm one, but the bastards where closed so it will be this weekend before I can get it .
good news is my tires came today so i had them installed, car rides and drivers 100% better. the old tiger paws where 10 years old.

New Tires look good, Merry Christmas and hope the MAF works out ok.
The screen is important, if you could find a another one that would be best, as damage in any way could disrupt airflow in a bad way.
A FPR Check is always a good idea on older cars: https://www.gmforum.com/chevrolet-17...ploded-309726/
Would also recommend IAC Cleaning:
https://www.gmforum.com/normal-maint...800-v6-307092/

IAC works fine and responds rapidly;y to prevent the car from stalling during its fits. , right now i have the MAF disconnected and it runs ok, alot better than when its connected, Im going to hit the JY tomorrow after work, they where closed Christmas eve, ordered a new Hitachi MAF sensor off ebay new in the box, , found a crack in the top of the drivers side rad tank, so I ordered a rad and hoses. Spent most of the day washing it by hand and getting all the door jambs and trunk and hood jams cleaned up, got a new thermostat to go in, i think the one that is in it now is either stuck open or its a 180 degree one. car hardly gets about 175 unless its just sitting there idling. also found a broken wire going to the secondary fan so i fixed that and it works now, and I've checked the fuel pressure, all the lines and regulator are new after they replaced a crap ton of stuff after the UIM blew up. fuel pressure is 39-40 psi running with the vac line on and when you pull it off it goes to like 48-50 .

well after the replacing the maf thursday with a orginial GM one , it ran pretty good back and forth to work for 2 days, but friday i was coming home and opened her up and go it up to 115 , it started running rough, and I had a p1404 code, so i pulled the egr and it pintle was clean, it moved free, so i stuck it back on, rand like crap that night going down to my buddies, anytime you would ge tit under the slightest load it would have a really bad shudder and i was getting a code for #5 misfire, so this morning I moved the wire to No 3 spot and no3 to no5 sport, no change, so i swapped coils around and then it was giving me mutiple cyl misfire so i said screw it, went to the junkyard and pulled every 3800 maf i could find that i didnt get the other day, long as it looked orginal. and i robbed a set of coils and ICM off a 2005 lesabre, along with the EGR valve, car had been hit in the front so I knew it was runnig before the wrecj, and I found 2 full sets of almost new Belkin NAPA plug wires, grabbed them too along with a brand new IAC and tps off another car that looked like it hadnt been replaced long ago, and found a Blue ashtray for my car, just the color I needed. installed the front 3 wires, swapped the ICM and coils and replaced the EGR valve and she runs like a top now all for $13.00 .
Andone need a MAF sensor? lol

since a cant seen to edit my post.

Also took the cover off the Maf that came on my car that must have been a reman and found this wire that was never soldered on.