1988 Mazda B2200 Engine stutters while under acceleration.

I love my truck and just spent about 4 grand doing an engine overhaul, bored, rings, bearings, hoaned an all that good stuff. Well like my father always told me, "Once you change things from stock, it'll never run the same or last as long."

I've come to realize this. I live in Oregon an the state doesn't require smog emmisions so I got rid of it all except for the catalitic converter. The other day I noticed that when under full acceleration that the engine tends to putter and choke. Thought it was the cat so I took it out and sure enough it was almost completly plug up. Now it's clean an just another piece of exaughst. But it still is stutter and sounds almost like it's loading up. But once at a higher rpm it stops, seems like it's the begining of every gear.

I've traced all vacum lines an are connected and not sucking excess air. Timing is dead on, an the vacum advance is working. I've only modified the exaughst to a straight through design and the intake with a taller air filter. It's been fine for almost two years like that and just started. Oh an I also replaced the 02 sensor.

Could it be from the exaughst being straight through without the stock backpressure? I'm lost. Any suggestions will be appriceited. Thanks

Cody