Slow WiFi speed on MacBook Pro late 2008 (A1286) I'm using a cheap TP-Link WiFi router and i'm hitting a wall at around 30 Mbps.
I've tested with other laptops and they run fine to 100 Mbps.

I have Yosemite at the moment, and an interesting fact is that, in the past, i don't remember on what OS, i was able to hit 100 Mbps on WiFi.

Any suggestions regarding WiFi settings or chip firmware ?
Be sure you are running the latest version of Mac OS X ( get 10.7.2+)
Apply all available system and software updates available to your Mac from Apple menu > Software Update
Reset the WiFi Router
After you’re positive you’re on the newest version of OS X and have all software updates applied to the Mac in question, proceed with the solution:

Add a New Network Location &amp; Renew DHCP Lease

Launch “System Preferences” from the  Apple menu
Select the “Network” panel
Click on the “Location” pull down menu and choose “Edit Locations…”
Click on the + plus icon to add a new network location, give it a unique name, and click “Done”
Back at the Network panel with the newly created location selected, click on “Advanced” in the bottom right corner
Click on the “TCP/IP” tab
Click on “Renew DHCP Lease” and wait for the numbers on the left to repopulate, then click “OK”
Renew DHCP in Mac OS X Lion

You should now have a stable wireless connection under Mac OS X Lion 10.7.2.

For most users the wifi stability issue was resolved with installing the latest OS X Lion updates, but in some cases is seems that old network connection profiles brought the problem forward for to the newest OS update.