86 3.8 throttlebody fuel injection problem?

I have a 86 vert with the 3.8 V6 and the trottlebody fuel injection. It runs good except when it has run for some time it gets a low end miss. You can power thru it and it runs ok till you back off the trottle again. Most times a hi rpm run will make it stop. Any ideas what this could be? If it were a multi port I would suspect clogged injectors, but with a throttlebody? Got me! Any help would be appreciated!