PCM Device Advice

[jersey]

Hi,
My names Rich. New to the forum.

I came across an Ebay ad for a PCM device that claims to increase HP/save fuel by overriding the H3's computer. I immediately dismissed this as a 'sounds too good to be true...' item but then in reading through these forums I came across the PCM acronym a few times and now I wonder if the thing or anything like it actually works? I use a fuel additive now that gets me near 25 MPG highway (3 gallons = 74mi.) and if I can improve on that, I'd sure like to. Can some of you offer me advice on these devices and on any others that will increase my fuel savings, such as performance exhausts, air intakes, old ladies with tow chains on souped up scooters, whatever you think might do the job.

Thanks,
Rich in NJ