What should I do? P0507, P0300,P0304,P0171?

Okay here is my problem. I have a Ford Focus 2003 2.0L SPI engine and I got a check engine light on. When my friend put the scanner, I got four codes. P0507, P0300, P0304, P0171. I really don't know what to do anymore because I changed the manifold, the whole catalytic converter and the muffler. On top of that, when I'm driving at 40mph, my car starts to jerk(skip) a little. That happens everytime I hit 40 mph but once I'm at 50mph it stops skipping. What should I do? What do each code mean?

Please help me out.

Added (1). Oh and I just cleaned the Mass Air Flow sensor and the air filter.

What car models are similar to astra gtc?

I'm going to buy a car pretty soon. Of course it is going to be a used car.

What i'm looking for is cars that are similar in model like the new astra gtc, renault megane coupe and ford focus (new models).

Does anyone know any more?

These i already thought of:
- astra gtc (new 2014 models)
- ford focus
- renault megane (new models like the 2013 ones)
- audi a3

Speeding Ticket in Georgia with Incorrect Information?

I received a speeding ticket last night in Dekalb County off Briarcliff rd a little after the Fox5 station. The officer said I was doing 55 in a 35. When I asked him to show me the laser it said I was doing 54. My biggest issue the car information is completely wrong. I drive an 08 Ford focus light blue with Missouri tags. The ticket says 04 Nissan Maxima SE Black with Georgia tags and the tag numbers don't even match mine. Do I have a chance of fighting this ticket?

Ford focus 2000 1.8 petrol lights on chimes on start up?

When I start my ford focus after it's been stationary for a while the lights on the dash are quite dim and the lights on chime 'dings' a few times but she does start first time.
I've not heard the chime before on start up! I've checked the belts are working and all appears ok under the bonnet.
Could it be the battery? Alternator?
Please help. MOT due next month so I'm expecting a big bill.

Dim Low Beam on 2001 Ford Focus?

A few days ago, I tried replacing my headlight bulbs with halogen ones, but one of them burnt instantly, so I installed the old ones back. The problem is that now the low beam is very dim, I can't see anything at night. The high beam works perfectly (high and low beam are in the same bulb). Also, when I switch to the low beam, the high beam indicator on the dash is dimly lit. Any ideas on what the problem might be?

2008 Ford Focus radio and clock not working?

I went into the car yesterday and started it up. The "FORD FOCUS" came on the clock as usual, but after that nothing appeared. Then i attempted to use the radio and it wouldnt work. If i pressed random buttons(pushing in the ok button a bunch of times) it would sometimes pop up like 12:00. I checked fuse box and the fuses were good. What could be causing this?

FORD not standing behind their product?

I previously wrote about my issue with my 2012 FORD focus (transmission issue) I WAS TOLD BY THE SERVICE MANAGER AT FOED THAT HE WAS NOT GOING TO TAKE THE TIME NOR THE MONEY TO TEAR APART MY TRANSMISSION TO FIND OUT WHAT THE INTERNAL PROBLEM WAS!

2002 Ford Focus LX using a lot of gas?

I got the car a year ago. It has not much to it as I just needed something when I got it. It's proven to be really reliable and not once broken down as I've put on close to 10 thousand miles (for a total of 138000). I recently got a new job and have to travel about 40 miles round trip. The car has done fine on the trips but my average mpg has gone down drastically. I usually can go 2 weeks between fill ups. Now it's just 4 or 5, days until the car is really low on gas. I know it's old but I thought mpg was supposed to improve on high way driving. Do I need a tune up or something?