runs bad from 3500 and higher

I had a post on here about th epossibility of getting bad gas in my tank and can't seem to find it. Anyway, when I am driving it hard and get up above 3500 rpm's it will stumble and act like it is starving for fuel, or missing. Today I drove it to the store and drove slow and it drove fine. When I was coming home i decided to get on it hard and it stumbled above 3500. after that, when i would push the gas down, it would do it at all rpm's. this has happened before and i was thinking it was just because it was about 1/8 tank and my gas tank (sock?) was bad. i have a full tank of gas and it is doing it. new plugs and cap last year. im thinking it still has something to do with gettin gthe bottom of the damn gas barrell at sunoco a month or so ago!!! if it is a result of bad gas, what needs to be done? is it something else you think?

thanks
EDIT:
I pulled the codes so Richter can be proud I don't think either of them have to do with running the way it is though.

CODE 15- memory failure ECA prom failure (this may be why my radio loses power each time i start it up UNLESS I pop the face plate off first.

CODE 67- Neutral drive switch open AC on during neutral drive switch/ manual lever position sensoe is out of range/pressure switch closed

NOT sure what either of those codes are or fi they need to be addressed, OR if they can affect the way it is running!

jrichker said:

The code 15 often pops up on cars with an add on chip on the computer. If you car has an add on chip or custom dyno tune chip, this could be the source of the code 15.

Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests. You can generally ignore this code, since it has no effect on engine performance.

The computer wants to make sure the A/C is off due to the added load on the engine for the engine running tests. It also checks to see that the transmission is in Neutral and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the car from being driven while the computer is in test mode. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.



The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis.


I would pull the TFI module off and have it tested at your local auto parts store. Bring along a hair dryer to heat it while the test is running. The failure mode for TFI modules is a high speed misfire when hot.

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thanks for reply. so it looks like i am still trying to figure out the stumbling after 3500 deal is. it did not do it today at all. very strange that it happens only sometimes! where is this TFI module located? I know I'm dumb