2001 Toyota Sienna, codes P1137, P0305, P0303, P0301, P0303

Hi, My Sienna has the engine light on for about couple of months now and it never bothered my until I removed the battery terminals and now just cannot go uphill fast as it used to and the gas pedal or even the overdrive does not help much. I took it to autozone yesterday and the guy pulled the following codes. Where should I start first to try to fix the problem?
codes P1137, P0305, P0303, P0301, P0303. Code P1137 does not have the Toyota listed on the printout he gave. Any help will be greatly appreciated.

have you ever had a tune up done?

Thanks for the reply. I just bought this van about 6 months ago and answer to your question is NO I have not yet got the tune up done.
I thought about it but did not take it for the tune up because it may cost me more if I take it to th mechanic with the engine light 'on'.
I guess looks like this is what you are suggesting to get done.

Well misifre dtcs are often caused by vehicles requiring a tune up as the forums can attest. Not suggesting anything just curious if it was done. If you're not going to repair it yourself then why know what the possibilities and repairs are. If you're not going to do the work then you also need a good technician as much as you need code definitions. You're assumption that it'll cost more because the light is on is kinda outdated because almost all drivability related repairs and services stem from the fact that it's on. History has shown that most customers won't service or repair there vehicle until something is staring them in the face. Hence the light.

I do intend to do it myself this weekend but just in case if I cant then will take it to the mechanic since I read that the back three plugs are not easy to replace. I have done the tune ups on my 4 cylinder Honda but I know v-6 is not going to be that easy.
I will keep you posted with the results so others could benefit with the resolution.
Thank you.

I did replace the spark plugs (Iridium) over the weekend but it did not correct the problem that I am having. It is not picking up the power especially going uphill. I was thinking of replacing the fuel filter also but could not locate. Can you please point me where is it located? or what should I do next? Thanks in advance

I don't think it's going to be a fuel filter. It looks like one bank is misfiring(cylinders 1,3,5), but not the other bank. The P1137 code is a manufacturer specific code and it relates to the O2 sensors, and although Im not sure what it is for specifically (I can't find that code definition for Toyota) I do know that it points to a problem with Bank 1, which is the bank that is misfiring on your engine. So, forget the fuel filter for now, it won't fix the problem. You're going to need to take it in to the shop. It's likely a Bank 1 O2 sensor fault, causing the fuel trims on that bank to go way out of wack.

Thank you so much for the reply. I will now take it to the shop for them to look at.

Yes, and let us know what fixed it.