SparkPlugWires, Does it make a difference? Options

[sapperk]

Does the size of the spark plug wire really make a difference? 5mm - 10mm

who has 8mm or bigger, where did you get them, and what did you pay for them?

[97GTinKC]

they wont make a difference IF your old wires are good, the thickness of the insulation means nothing for performance, it just takes longer to go bad, OR if you have a super hot aftermarket ignition coil it might make the wires last longer before they break down and start arcing and mis-firing.
My personal opinion on this is along the lines that all the ignition does is ignite the fuel, its the fuel that gives you the performance, granted stock ignitions may not be adequate for a hi-perf race engine, higher compression and diff advance curves needed etc. but not too many of us are driving those on the street. the stock Celica ign is way better than even the old "performance" ignitions of the 60's and 70's cars...as long as it is functioning correctly. I dont think you would notice enough difference to justify the costs on an otherwise mostly stock engine with a CORRECTLY working stock system.
(And the best test I have found is to look under the hood on a really dark night and rev the engine, if your wires are breaking down, you will see arcing along the wires, I have even had people take their cars to the dealer and get them diagnosed and not catch bad wires )
So people put new wires on, not realizing their old ones were bad, and say, Yes it really has more performance than stock wires, not to rant, but I say all the above after having worked in a parts store for more than 12 years, some of these company's perf claims just make me laugh. OK I feel better now,,,