Removing items reduces weight by:
Passenger seat (Electric,no heater): -45 lbs (inc. bracket)
Rag-top w/ assorted hardware: -40 lbs
Spare Tire and Tools: -30 lbs.
Rear Speakers w/shelf: -8.5 lbs
Carpet over engine hatch(heavy insl.): -7 lbs.
replacing with lighter components:
B&B 2nd gen. muffler: -25 lbs (from stock "S" muffler)
Sparco on the driver's seat -30 lbs.
replace 18" turbolook wheels -20lbs , 5 lbs per wheel (unsprung)
Carbon Fiber hood - 20 lbs.
Carbon Fiber trunklid - 8 lbs
CF doors -50 lbs + weight of roll cage vs stock roll hoops
so about 130lbs can be removed for free
the next 150lbs is more expensive
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Even with all this work done, the Boxster will weigh 2600-2700 lbs which is a lot more than a Lotus Elise.
Keeping the stock seats and a working ragtop, and I assume radio, air conditioning,etc. you can reduce our weight by 1 large bag of dog food for free and 1 more large bag of dog food for $1000.