well i got the codes: P0171 (too lean) P0300-P0304 (failed cylinder)

 

o2 sensor on exhaust manifold im guessing was fried? Chime in please

 

Are you getting all 5 of the 300 codes? So 300, 301, 302, 303 and 304? That should mean that :

300 = More than one cylinder misfired
301 - 304 = all 4 cylinder misfires (301 means cylinder 1 misfired for example)

So I would say that the 02 reading that the AF is off could be a valid code, since you are seeing misfires on all cylinders. It could also possibly be that the 02 is bad, affecting how the car runs. The car should still start up fine though if it were the 02.

Another thing that could be part of the issue would be the coil packs, but I would be surprised if all 4 of them got it, but you never know.

But.. although you were welding (making you go to that cause first.. which is the natural way to think) on it, there could be another cause. I am guessing you had the intake off when you did so. Have you double checked all the vacuum lines? If you have a vacuum leak, the car should read lean and can misfire. It could be a simple matter of you accidentally leaving a vacuum line off. Check the simple first!

 

Actually just saw that someone already mentioned the Vac hose, but it doesnt hurt to check all the others on and around the intake as well.

 

well all the vacuum hoses were checked by a family friends shop down the street. Also when the bracket got welded the intake was kept on the car and nothing was removed.

The car does start up now on the first try it just needs to be warmed up. Drove it around a little and it sputters for the first 3000rpm than after 4000+rpm it drives normal, but since it has the lean code im worried of test driving it even more.