Driving car purchased in Mexico in the U.S....

We live in Zihua about 6 months a year (permanent residency visa now) and purchased a Mexican car a few years ago. We are now on our third drive back to the USA in that car with absolutely no problems entering USA or getting it back into Mexico. Have driven it all over the western states and only once been questioned.
The first time out we purchased USA liability insurance before crossing - this was a bit of a problem because all companies required us to have a Mexican Driver license. After a lot of confusion and help from some locals we finally found insurance without the license. Mexican D/L is very easy to obtain so get one.
On our second trip we discovered that our Mexican insurance policy included liability and limited collision coverage for USA and Canada so border insurance was not needed unless you want greater coverage.
Be sure to carry all your insurance and ownership documents. We were stopped once at a Fish & Game checkpoint in rural New Mexico and the Ranger required everything before letting us go.
Another poster mentioned clogged injector problems. We don't trust the cleansing quality of Mexican gas so we always bring back a few small bottles of Chevron's Techron additive and add it to our tank periodically. No problems so far.