Hi, welcome to the board! Where ya from; you can edit your profile if you wish, via your 'my home'.

First, forget what your friends have to say for the moment; do some old fashioned preventative maintenance FIRST.

Change ALL your lubes; remember to remove the FILL plug FIRST, or you'll be sayin bad words. Get a 6 pt 22mm and 24mm socket for yourself.
Inspect/lube u-joints; don't overlook the 'hidden' zerk on the front D/L.
Inspect brakes and ebrake cable
Change fuel filter and air filter
plugs/wires/cap/rotor-- replace.
Inspect/replace belts and hoses as needed.
Inspect suspension and axles for leaks and cracked leaf springs
(others will chime in I'm sure) <img src="/forums/images/graemlins/kewl.gif" alt="" />

Click on our Toyota section above, and you'll be transported to our tech articles to further acquaint yourself with your truck. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Sounds like you have some doubt in the seller; all the more reason to go thru the truck. <img src="/forums/images/graemlins/shame.gif" alt="" /> <img src="/forums/images/graemlins/shame.gif" alt="" />

We also have a couple of factory service manuals already sticky'd here, so have a nut.

Also bookmark these sites:

www.engnbldr.com
www.4Crawler.com
www.yotatech.com
www.autoshop101.com
www.1sttoyotaparts.com
www.rceng.com if you REALLY decide you MUST do something with your injectors.

On the L/B swap, did that include or exclude harnesses from the donor vehicle?

Please better define "won't run very good"--what's it doing?

Could be as simple as the TPS being out of adjustment.