How could you lean the engine out by making it breathe better? I have been running TPIS long tube headers for over a year, and have scanned my car several times and I haven't had a lean condition.
Vettefan87, I'm with Midnight 85 on this one, if for no other reason aside from me experiencing this exact problem on another vehicle.
All of my previous Chevy vehicles were carberated (and usually nitroused, lol), so I haven't played around with an "electronic" GM vehicle...ever, but for the last 10 or so years I have been playing around with several supercharged and nitroused Fords, both my own and others that I have tuned. I had a 94 5.0 Mustang that was somewhat of a hybrid (or bastard) as far as ecm's was concerned. It wasn't quite an OBDI, but yet it wasn't quite an OBDII either. Anyway, the car ran very well, but always felt like it flattened out at 4500 rpm's or so. When I added better exhaust (headers, off road X pipe, straight thru mufflers), conical K&N w/aftermarket piping, and underdriven pullies to free up some rotational mass, the car ran GREAT at lower rpm's, but still seemed to go flat up above 4500 rpm's.
I finally had all but given up on the car, and decided to try something simple, on a whim. The item was an adjustable fuel pressure regulator. The "stock" base pressure was 38psi, and I set it at 45psi just to test my theory. Car immediately revved cleanly to 5800rpm's or so, even with it's stock restrictive intake manifold and wheezy cylinder heads. At "normal" driving times, car was unchanged since the ecm adapted itself, as it should, to the amount of air being ingested. On the Fords, it turned out that at WOT, the ecm doesn't control fuel in nearly the same way it does at cruise, and idle. It has set parameters, but when the "mechanical" setting (i.e., fuel pressure) is changed, there's no way for it to over-ride that with the factory ecm. You'd have to have some sort of aftermarket tuning via a chip, or piggyback tuner of some sort.
I have no idea if our Corvette's work in the same fashion, but if they do, then Midnight 85 is correct in thinking that I will get a lean condition. It shouldn't change at "normal" driving rpm's, but at WOT there will be a lean condition. Like I said...this is IF the Corvette ecm works in the same way. I'm going to believe that it does, until someone proves it different, since my 85 acts the same exact way my old 94 Mustang did when I made it breathe a little better. It runs great at cruise and part throttle, but seems to "level off", or "flatten" at wot. I know the stock intakes seem to be an issue, but if you're making the engine breathe better, it absolutely needs more fuel to make anymore power.
A crude and exaggerated comparison would be a nitroused or supercharged engine. You spray a 200hp shot of nitrous or pump 15# of boost into your engine and don't add anymore fuel, you lean out severely, usually break or hurt parts and make no power. Add the proper fuel to either equation and the car screams...That's why generic chips like Hypertech usually don't work. No way possible to tell how efficient engine "A" is, as compared to engine "B"...
Take my stock motored 85, have the best tuner in the world burn a chip for it, then let me add a nice ported set of heads, long tubes, open exhaust, custom cold air intake setup, etc. and that tune is way off for no other reason except you'll be pumping a ton more air into (and out of) the same engine. Again, an exaggerated example, but the same basic theory as a K&N, open lid, and nice breathing exhaust will be acting on my stock setup.
Hope this helps.
