I'm about to get my spark plugs replaced on my 1990 LS400 and was looking for some feedback.<br>I've heard that NGK is the way to go for Japanese cars but I've also heard that Bosch Platinum IVs are the best plugs on the market. They both cost $6.00 each.<br>Any advice?.<br>P.S.:I'll post pics soon<br><br>1990 LS400, 18" Lexani Solars on 235/40/18 Sumitomo HRZ II, clear bumper lights, 2 JL Audio 12" W3D2 Subs with 400W PPI Amp.

I got some BOSCH Platnium +4, and guess what.<br>I seem to get a "engine miss-firing " at cruise<br>speeds , I dumped the old NipponDenso back in and it seems to have went away.

Hate to ask the obvious, but did you check the heat rating and the gap on the Bosch plugs? I've had bad luck with Bosch and prefer the NGK as they typically run a bit cooler and are more reliable overall... good luck!

Hey - you may also want to pull the fuse for the EFI and leave it out for about 3 minutes. This should reset the ping/knock sensors and will cause the EFI to "relearn" your engine characteristics. That may also solve your problem with the Bosch - but I really think it's either a gap or heat rating problem.

Just an idea. If you are going to spend that much money and are willing to be a guinea pig, why not try Iridium spark plugs ? You can get one for about $8-$10 on eBay, online store like http://www.sparkplugs.com or at some auto parts stores. The Iridium plugs are SUPPOSED to last longer than platinum but have even less electrical resistance than regular copper plugs (platinum has even higher resistance than copper) TFW