2uz-fe
I almost pulled the trigger on a 2008 Sport V6 4x4, but I am glad I kept my 2005 Sport V8 4x4. The other members here with V8's have all had nothing but great things to say about the engine. Not saying the V6 is bad at all, but I think I'm really going to be impressed with how far this 4runner will take me.
Also, my Borla wouldn't sound the same on a V6. Recently I have been getting tons of compliments with how my 4runner sounds. I don't even have the Volant CAI on there. I removed it and put the stock airbox on for my CA SMOG, and kept it on for the wife while I am deployed. It has the reusable K&N air filter installed, and when I first got the 4runner I removed the HC filter. I probably didn't need to do that, but I was eager to perform my first mod.
Back to the OP, I am so glad I kept the V8. Thank you to everyone who had posted about how their experiences with the 2UZ-FE. It really made me feel like I made the right choice. I can't speculate on an engine with 150,000 miles but I hope it all works out for you. To be honest, it all comes down to the previous owner and their care for the 4runner. Good Luck!