Mac Pro 2008 3.1 Airport Wi-Fi Issues

[Yaoi-Wiccan]

I recently just got myself a 2008 3.1 Mac Pro. The room it is located in does not have a wired internet connection access, only wifi. I bought a used Airport extreme card that I installed. I used anntenas 3 and 1 to plug into the card. I was able to connect to my network and it says I have full signal strength. Problem is there is almost no data coming in. Now sometimes it will work as it should for a few minutes but then take 10 minutes to load a few seconds of a YouTube video. I ran the diagonsits on the wifi signal and it came back all fine. I also did a test of having an old laptop run it's wifi signal to the mac though sharing of the Ethernet port and it works just fine so I do not think it's an issue with my router or internet connection. Has anyone else had this issue before? Maybe I didn't set up the airport card correctly? Thanks

 

[Yaoi-Wiccan]

Should I be using a Airport card with the three antenna points on it over the two point one I am currently using?