I just had a shop with a very good reputation install a used TCI 3000 RPM stall, lockup converter in my 1988 GT. Before the installation, the converter was checked for any flaws. I just moved up from a 2200 RPM converter, and before that from stock. This change however was bad. It studders (feels like a miss) at low RPM, badly. It takes a heck of a lot to get it moving, it doesn't like shifting, it hates idling in drive (500 RPM & surging) and it burned 1/4 of a tank on a 5 mile drive. None of this stuff happened before the change. I just paid a crapload for the installation & converter check, and I want to know everything I should before throwing it back at the shop. Ideas?