Have removed header and Alta intake.....using stock components......no seemingly loss of performance. Plus, easier to smog. Replaced Marshall water temp gauge with a Marshall oil pressure gauge.
If you took out the Alta box, you probably gained performance... Which header was on? I'll give him props for changing from water temp to oil pressure, I'd much rather have oil pressure, and oil temperature, if I could only have two gauges.
Still have it....still runs looks great! 101,000 miles. Just need to replace the front bumper, some ding dong backed up into it and left Wife has sold her Mini.