The White Rain Mouse cans I use are 1 3/4 x 6 1/2" long. Did you just cut the 1 1/2 " a quarter inch at a time or did you whack it all off at once. I tuned an O.S. 32 to a MCM this week and I only took of 3/4 " in 1/4" incriments and it turned 15,000 rpm with an APC 10-4 prop. If you cut it all at once you might have cut off too much and went past the sweet spot. If you did you have ruined the header for tuning that engine. You can salvage the header by making another MCM and making the big end that goes into the header about an inch longer than it is supposed to be and then when you tune it cut the MCM instead of the header. Also I didn't have much luck with the A3 glow plug. Iwent to the#8 O.S. and the low and midrange was much better.