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Sorry, I checked the 2000 4.3L S10 in the yard and don't know how the oil fill tube is removed. Our Bravadas have the 4.3L Vortec V6 until 2003.
Lack of sufficient fuel pressure has been the problem with many and likely is your issue too.
A fuel pressure check is in order, the pressure spec. is 61-65psi.
There are test kits available at most auto parts stores for around $40 and Harbor Freight has them at a much lower price.
Here's where to check yours,
Be aware that if a fuel pump replacement is in order, use only the Delco brand pumps as other pumps appear to be failing, often as soon as they're installed.
Let us know what you find.