I've also used it to great effect (combined with a hi viz jacket) to slow down speeders on our road! Mine in black looks exactly like a speed gun!
Mine had the lenses and the cut outs for the lights but no lights in it. So when I deleted the bumper ones, I just picked up the light housings off eBay and connected up the wiring.
I wanted to stay UK correct, but given that the modern rubber is nowhere near the quality of the original items, I wish I had ordered my Harrington bumpers without them (they did send me a second set, but they too only lasted about 3 years before cracking). Unfortunately the Harrington bumpers have been scraped / roughed up at the factory behind the rubbers (can't figure out why), so without some serious machining / polishing, it's not a case of just taking them off and putting stainless bolts in the holes. Something to bear in mind if you ever order stainless steel bumpers.
I'm with Farmer Paul here. You can't possibly install the 123 and hope it's aligned properly with TDC etc. The way I did mine (with the assumption that the crank pointer was accurate) was that I set a curve with 10degrees at every rev, set vac advance to zero and used a timing gun to validate that is what it was doing. That way you eliminate potential for "mech advance". Popping when you put your foot down is generally an over-rich backfire (due to mix, or timing or spark plug not firing - I had the not-firing issue when my Magnecore leads failed) or timing as mentioned already.
@Carl Platel ...
As for colourtune, having owned / used one. I'm not a great fan. It's probably a good tool for stock engines where the N27/N54/SM needle profiles will mean that setting up at idle takes care of other conditions, but if you have engine mods / non-stock exhaust system, then all bets are off.
Yes you can see what's happening in the cylinder with one of those, but you're only setting up the car for two out of many load conditions (namely idle and fast idle), in the hope that your tune is perfect for cruise, pickup and Wide Open Throttle (where it really matters). IMHO you should really invest in a wideband O2 sensor; which is WAY cheaper than rolling road time and you get to see what the car is doing under real driving conditions. To give you an example, you may set it up perfectly for idle / fast idle using colourtune and find when WOT, at certain revs it is too lean, which will cause audible and inaudible ping / knock.
As mentioned already, use the official SU oil - it takes the guesswork out and one less thing to worry about for peanuts.
https://www.ebay.co.uk/itm/186104053625?
Given your description, it sounds like bogging down, my advice is (as been said by others too) :
1. Validate with a timing light, the 123 setup - to ensure you are getting what you see on the app
2. Ensure all the ignition system works as it should - e.g. every plug is firing / test the leads with a multi-meter for continuity, check coil health etc. With 123, I found no end of issues with the supplied Beru caps but no issue at all with the Bosch offerings.
3. If you find the timing / ignition aren't the cause then look at the carb tune - if you are on a stock engine, with SM needles, I found 2.5 turns down on the carb jets was quite rich on an L26, so start with 1.5 turns and incrementally add more if running lean at WOT, or you find the accelerator is over sensitive / jittery when on the transition from slow cruise (town speeds) to light acceleration.
4. And seriously consider getting a Wideband sensor. I would have saved a lot of money if I had done it earlier in my ownership. My preference is Innovate, but AEM is another brand many have used:
https://www.speedingparts.co.uk/p/e...nnovate-mtx-l-wideband-sensor-and-gauge.html?
Good luck and enjoy the Z - once under your skin, it never leaves you!
I’ll get a colour tune I’m I made recently fitted the 123 ignition system and no I’m not totally convinced it’s correct it would make sense that the timing is incorrect, I’m having an exhaust made and I found a old school rolling road chap so 
