think the whole point is he wants a 16v beater so they cry when he tells them its an 8v
Thats not hard to be honest, 16v is not the quickest engine in the world 
Yuo're getting boring now

Same amount of work on the better engine will get you better results

On a serious note - save weight gain performnce. As Chapman at Lotus said add lightness.
As you might know I have a Mk3 16v which is probably as light as it can go without major bodywork modifications. But a well sorted Mk2 in the same sort of modification will be faster than mine because it is lighter. Horney's Mk2 8v is well sorted with a ported head,Cam, lightened flywheel etc is more tuned than mine and can hold its own. DH's Mk2 8v syncro with its ported head, cam, and lightened flywheel etc will hold its own. Danny P's Mk2 Syncro with its ABF engine etc is the same.
So a Mk3 8v with the right work will also be good with the right work and the right weight reduction. Power to weight ratio is one of the biggest factors in going fast, but you need the right chassis to start with. Have you ever gone up against an Elise with 160bhp? God they can go round corners. Seen them show up big hp cars.
Sort your weight out, sort your chassis and handling, then go for the power.
On topic the chip Rtech did for me was better than the standard one, better than the ebay ones, and I'm sure if they set it on their rolling road it would be good.
So I've seen tuned Mk2 8v's go well, so Mk3 8v's should be able to get the same performance but only the weight will go against them.
Best performance modifications I have made on my car have been to the handling and not the engine. Arb's and aggressive alignment made a world of differance.
Drive it, tune it , enjoy it, whatever it is.
Paul