In the past couple of weeks my transmission has started flaring quite a bit during the 2-3 shift. The tach will increase as much as 500 rpm during the flare. The transmission fluid is at the correct level and is bright red (I changed the fluid, filter and gasket about 17,000 miles ago).

I've searched and it looks like the flare is most likely caused by either a vacuum leak or a bad K1 spring. Am I correct that these are the two most likely culprits?

If it is a vacuum issue, wouldn't it also affect shifts other than 2-3?

On a related note, about seven months ago I removed and blocked off the EGR. I plugged the vacuum line leading from the black box on the valve cover to the EGR, but otherwise left the black box untouched. Since this box only controls the EGR, can I remove it entirely and plug off the lines leading into it?