Not your normal ruff idol.
 

I changed the plugs the other day (week or so ago) and my mpg droped from 300 a tank to about 260. The car doesn't feel like it's running ruff but when in neutral and you rev up to 2500 rpms I can feel it sputter. I wasn't shore that them two plug wire with the boxes on them fully snapped into place. How do you check it.

Were they perhaps aftermarket wires? Sometimes some varieties don't fit as well the OEMs Just wiggle the puppy while pushing on it is about all there is to do...then try it again. Did you get the plugs properly gapped? Just guessing, sorry not more help.

Pull 'em out, check the gaps and be sure to check if the plugs have been fouled in any way.

Also....whenever I change my plugs, I also change my wires....

Is it really necessary to change the wires in our cars at all? I put the Nology Hotwire kit in my car and I think they're pretty useless. Supposedly they give you better fuel mileage, increased HP and torque, and better acceleration along with higher top speed ... but all they did for me was decrease gas mileage and give the car a high idle (2200 rpm to be exact) when it's in park or neutral.

So that leaves the NGK wires which may actually do something, but in reality wouldn't the stock wires be just fine? I didn't mean to shut you down Phil, but that's just my 2¢ on the wires ...

I left the stock wires on and the plugs are some platinum (?) plug that doesn't need gappin. Has anyone changed the plugs and used the factory wires? If so when you put the middle two back on did you fill it snap on? I didn't.

Oh ya, I remember now. They are bosh platinum, heres a link about them.
http://www.boschusa.com/AutoParts/SparkPlugs/Platinum2/

I have yet to do a tune up on the car (plugs and wires), but on my others, it was NGK & matching wires.

Do you have a loose plug? Recheck the torques.

Then re-seat each plug using the Dielectric grease to maintain good contact.

Last, could be a bad plug from the factory - not impossible! ;) Maybe swap the 'best' old plug back in one at a time in each cylinder - noting if the performance suddenly gets better.

Look at the ends of the plugs when you pull 'em. One may have been dropped - mashing the end and closing the gap.

The sudden drop after changing the plugs is the clue - don't swap wires yet.

(And when you do change wires - just get stock. They are fine. )

It runs pretty damn good. I'll recheck every thing this weekend and let ya know.

from what i understand, wires will last a long time, and there shouldnt be any big reason for a upgrade unless your car is running on a mission critical level. You would get proven performance just by upgrading your grounding system on most cars as opposed to the ignition upgrade. (source here for example http://importtuner.com/tech/0308it_pptalon/ http://importtuner.com/tech/0405it_300zx/ )

OEM stock wires should be fine.

Plus Meh, hard to say, we visited the plug question in the past and one guy will perfer this one over that one, one is crap, or crappier then the other. pick a brand and stick to it. but you cant go wrong stick with stock. Unless your running an advanced setup there is almost no point with the upgrade.

I actually lost lower end power on my car because of my bosch plugs but gained on the upper end, but it was almost hard to prove that its a good thing.

NGK is stock for our car, its proven and authorized by mazda stick with that.

Do a search on the forum here if you want to read what I came up with in my review of NGK Vs. Bosch.

but its one of those mad science experiments that doesnt mean anything to the average guy with a few or no mods.

Bottom line, Run Bosch for higher end power. but if your using nitrous and using the platinum version of the plugs you may have problems with the bonds weakning and breaking off in the cylinder. There are Europe and Aussie plugs made of different metals of the same design such as Silver, Nickle, etc. I beleive those will hold up to Nitrous applications. Rod was asking me about it, Rod did you ever order any of the silver ones for your ride?

One thing i will say, if you happen to get a good pair of the Bosch +4s they will last you forever. inspect them every 20,000km but you will see that the centre node holds up well and the 4 points look to wear well over time. they could out last your wires.

but i wouldnt push it that far, the centre node has been known to crack over time once you see that , chuck it.

Tests of the NGK irridiums are equally as good, and were the opposite of the Bosch plugs on the dyno. but the gains were barely mentionable.