I swapped a 383 for the 350 in my 1988 Iroc about 8 months ago. Ever since then it has been one small problem after another. In the past month or so when I floor it, the shift from first to second takes way too long. It almost always stumbles like it has a rev limiter. Someone told me it could be the torque converter. Is this true or is it something in the engine. I have a stock cam and fuel injectors. The plenum is is ported and I have an adjustable fuel regulator. I also have an aftermarket chip from fastchip although it was bought for the 350. I would be extremely thankful for any help. This isn't just annoying it's embarrasing.