IMMEDIATELY I noticed an improvement

I came across Pulstar spark plugs in some 4x4 enthusiast forums, and after looking through their website I was so impressed with all the background information provided (both the level of scientific analysis, and the sheer volume of empirical data) that I decided the generally high-price was justified, and I would try the plugs in my own vehicles (a 1989 Landcruiser and a 1997 4Runner). IMMEDIATELY I noticed an improvement in throttle response; it was particularly obvious in my 4Runner which suffered from an 'engine stutter' issue that I had been trying to properly diagnose and fix for about a year. Right away, the stutter issue went from being noticeable in approx 15-30% of certain throttle situations to scantily noticeable at all, and when it is noticed it's only in approx 0-5% of the same throttle situations. I also noticed a significant improvement in fuel economy. I am almost religious when it comes to calculating my overall fuel economy for the last tank of gas after every fillup (I even know exactly how much my different-than-factory-sized tires impact odometer readings on both of my trucks, based on distance comparisons between odometer vs. GPS data) and prior to changing the spark plugs I would average between 16-18 MPG (often in the high 16s - mid 17s, and only reaching 18+ on tanks that were nearly 100% highway miles at cruising speed) in the 4Runner. Now, since installing Pulstar spark plugs, I've filled-up 4x tanks of gas in the 4Runner (none yet in Landcruiser) - and on the first three (which were no different from my normal weekly commute to/from) I averaged 18+ MPG (up to 18.5) and on the last tank, which admittedly was quite favorable in that it was 260+ miles all on the highway at cruising speed (not more than 75mph) and coming from Bishop CA to Los Angeles CA (an overall drop in elevation of about 3,000ft) I averaged an ALL-TIME-HIGH overall 20.1 MPG!