Need some help

I have a 1988 k5 blazer with a 350/th400 combo. The engine is bored .030 over, has a bigger cam, roller rockers, and a holley 770 carb. The th400 has a 2500 stall torque converter.

The truck has run and drove perfectly for a little over a year now, just recently I've been getting a stalling problem. After I let the truck get to operating temp I'll put it in drive and it will drive perfectly, the problem is when I stop. If i come to a complete stop and let the truck idle in drive (or reverse) it will idle for about 30-40 seconds then start to bog down and eventually stall. It will start right up again and idle in neutral normally. Put it in gear and it will eventually bog down and stall again.

Like I said this has just recently started happening. I have a bad feeling that the torque converter is to blame but its less than a year old. (I switched from a 4000 stall converter to a 2500 stall converter in june of this year) Plus the th400 is not a lock up converter and I don't hear any noise coming from the trans to indicated a worn or seized bearing.

Does anyone have any knowledge or ideas on a problem like this?