by panic » Tue Sep 02, 2008 8:56 am
By "upgraded" I assume you mean 1-2 ranges colder plug? There are no grades as to duty or efficiency in plugs - some just cost more $$$.
You're probably at or close to 100% duty cycle now on the injectors, or you will be if your map is adjusted. This means you either need more fuel pressure (not necessarily a bigger pump - some can be set to higher pressure), or bigger injectors, but you may not need both. Before you buy injectors you have to know what pressure you have (or will have) and how much power the engine's got to determine the size. Too big isn't as bad as too small, but it's not good. Someone with a very similar set-up can tell you what size, be sure they're compatible with your stuff (not just Toyota etc.).
What's important is that you not use hard throttle until you fix this, or you're going to break something expensive.
My guess: if you go to the dealer, they have no idea whatever as to what to do, so they're just going to charge you for inspecting/removing/replacing/adjusting everything on their long service list - whether it fixes your problem or not. Huge $$, same problem.