I thought about getting one of those battery stabilizers, the one by Sun Auto is mad expensive, I found a few knockoff ones but not sure if they really do the job

Here's the one I found at a local store: http://fore6767.hp.infoseek.co.jp/page104.html

As for the idle, I just changed my Spark Plugs about a month ago, could it be I didn't torque them correctly? I used a torque wrench to the correct torques..

How much would new fuel injectors go for? Are they easy to change myself?