Engine Help!!

I cant figure out what's causing all these problems in my Mustang

It's a 2000 Mustang GT, completely stock except it has a cold air intake and a ford racing intake manifold. (recently installed)

for the first 2 weeks after the manifold was installed the car was running better than ever. Unfortunately, it started misfiring when I was on my way back to lsu.

Here are the trouble codes i'm getting and what they mean according to auto zone
p0171 (fuel trim bank one condition)
p0174 (fuel trim bank two condition)
p0302 (misfire on cylinder 2)
p0308 (misfire on cylinder 8)

New spark plugs, new coil on 8, fresh oil, needs refrigerant but i'd like to get the car running properly first.

Anyone can take a guess?

I would like to make taking it to a shop the last option. After tuition and rent I just cant afford it right now.

Noobz347 said:

Sounds to me like a vacuum leak.

Click to expand...

How do I diagnose that and repair?

Thank you for replying by the way. I appreciate it.

Noobz347 said:

Simplest method would be to pick up a can of engine starter from where ever is closest. Spray it lightly around the parts that you removed/installed/reinstalled. If the motor stumbles or idles up, then you've found the area of your leak.

Pulling unmetered air into the intake can cause your first two codes. Cylinders too lean on fuel to properly ignite can cause your other two codes. My guess is that you have a vac leak around your manifold since only two cylinders are misfiring. Probably around cylinders 2 and 8.

Click to expand...

Thank you so much! i'll give it a shot this weekend.