believe it or not the resonators being removed are what is responsible for your seat of the pants power increase not the cat.you have the old faithful "k" jetronic and there are so many potential issues that it's diff to know where to start.unless replaced recently the warm-up pressure reg could be a problem or the vac lines going to it.you need to fit the "k-jetronic" pressure gauge to the system and watch pressures warm at idle and what happens when revved.that engine was pretty powerful at 240 hp. david poole european performance dallas tx.