350 tbi bogging in mid to high range

Hi,
I have the following: rebuilt 350 with roughly 45K on it. 1988 suburban tbi
The engine has started something weird that's slowly getting worse.
The engine runs just find until you press the gas peddle more then 1/2 to 3/4 of a inch down, at which point the engine makes a bogging sound, it almost sounds like there is a exhuast leak under the hood and I have no power. On a recent long trip, the problem got so bad that I had to downshift going up hills and I couldn't pass anyone as the engine just couldn't do anything (lucky for me the v-8 could keep up highway speeds mostly just above idle). If I did press the gas peddle down, the engine would lose power and then the service engine soon light would come back on. It would eventually go out again. I have thoroughly inspected under the hood and the exhaust is fine, and all the exhaust manifold bolts are tight. I just replaced the airfilter too. The engine doesn't backfire from leaning out, and I don't get any black smoke from running too rich. The engine seems to do this just after it's first started and then once it gets really warm, on a long trip. Could it be something electronic?
Any ideas here on what's the problem?
Thanks,
Clint
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Internal leaks in the TBI unit. Think spark, fuel, and air.
Have a great one!
Bush
On Tue, 08 Jul 2003 22:55:11 GMT, "Martin Riddle"

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I'll stray from the pack and say Catalytic converter(s).
Also, what code was set? Pull codes from the ECM, it would give us a lot more to go on.
To pull codes from an OBDI(pre-96) car, follow these instructions:
Locate your ALDL connector. In an 80's Chevy half-ton truck, it's probably under the dash somewhere near your left knee. Take a jumper(paperclip works just fine), and insert it into the ALDL connector's A&B pinouts. A&B are the right-most upper 2 pins on the connector.
Insert jumper. Turn key to RUN, not START, and pay attention to your "check engine" light. It will begin to flash.
It will initiate code-reading by displaying code 12 3 times in a row. Stored error codes follow the 12s, with the code reading terminating with another set of 3 12s.
Sam

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