I purchased that kit from Hesco about 2 years ago and have had zero issues with it. At one point i was having an ignition problem about 8 months ago and thought the CPS was to blame and gave Hesco a call to see if i could purchase just that sensor. They responded with a respectable offer, if it broke that soon we'll replace it. Low and behold it was my ignition module that went out. So i would have to believe they would be kind enough to sell you just a single sensor if one failed in the future.
Little low down on the goods that came in my kit. Comes with a CPS with the magnetic pickup shifted forward thus advancing your ignition timing 3 deg.(according to Hesco), a new water temperature sensor, manifold air temperature sensor, and EGR block off plug. As Mgardiner1 stated, the temp sensors do have resistors inline with them to trick and make your computer think that your intake charge and your over all engine temperature is cooler then it really is causing it to run richer then usual. Like i said, i for one purchased this and am currently running all components on my 88' w/ 250k miles. Because of the tired engine i did notice a increase of over all power mainly in the top end were i know the engine has tendencies to lean out, but it also runs richer then i would like @ idle and i believe has had an effect on my throttle response. But keep in mind this is on an engine thats probably burning more oil than fuel and is in desperate need of the stroker that awaits it. I've considered removing all these components when the stroker is install but haven't decided yet.
I should probe those resisters hu?
I would probrably save my money, kick my passenger out and remove my back seat for the same amount of performance. Nothing against Hesco, i actually gave them a fair share of money for some of my stroker parts and they do offer quality products.