I have been running a Jacobs system for almost 10 yrs now and have very little problem with that wasn't taken care of by Jacobs(now Mr. Gasket). I am not sure what the HP gains are w/my rig, but the mpg is up about 1-2 mpgs w/than when stock, and over all performance is better wthan w/o. In the 10 yrs I have had it I have had to have the coil replaced once(no charge lifetime warranty same for the spark plug wires), and I have had to replace the cpu once at 1/2 the cost and free shipping(replaced the cpu after Mr. Gasket bought Jacobs). I cannot comment on the newer system. The most important benefit that I have found from the Jacob's, is its ability to fire up the truck when the battery has been run down from either extended use or change in weather.

As OOP'S mentioned headers are the best way to increase performance, it was the last upgrade I did on my 3.0 due to them not being smog legal here in CAli when I was doing the opther upgrades. The one thing to keep in mind that no one mod to a 3.0 is going to gain that much, it takes a combo of upgrades before you begin to see the benefits, the upgrades also aren't cheap I have spent about $1500 upgrading mine. If you are looking for large gains in power your only real option is to do a 3.4 swap, that is until someone redesigns the 3.0 heads(to allow for more exhaust flow) or figures out a way to put Camry DOHC heads on the truck block.