Didn't we already go over the spark plug thing?
Considering that my truck (98 Tacoma) wasn't meant for towing something as big as my trailer, it does really well. Also does really well around my town of 5,000, but also around much bigger towns. But it did take some of those modifications Steve mentions.
Although I have to admit, while ideally I'd have a bigger truck, after 5 years of towing with this setup, I've had no issues. Under powered, sure. But for a 20 year old truck that only started towing after it had 200,000 miles (now has 279,000), with still original clutch, engine, transmission...it does fine towing in town, fine towing in the mountains, stops when I've needed to slam the
brakes. Seems to be a perfectly adequate tow vehicle.