Big impact on page loading.

hi, i notice a big increment of loadtime of my site after paypal Responder installation. i check with p3 plugin profile and your pluign have a big impact on page loading: 88%. If i deactivate it the waiting time for first byte decrease incredibily. Is there a way to debug your plugin and discover what’s the problem?

P3 REPORT

WordPress Plugin Profile Report
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Report date: marzo 2, 2016
Theme name: Oltremeta
Pages browsed: 17
Avg. load time: 5.9091 sec
Number of plugins: 17
Plugin impact: 88.06% of load time
Avg. plugin time: 5.2034 sec
Avg. core time: 0.3900 sec
Avg. theme time: 0.2700 sec
Avg. mem usage: 31.24 MB
Avg. ticks: 18,104
Avg. db queries : 67.82
Margin of error : 0.0457 sec

Plugin list:
===========================================
P3 (Plugin Performance Profiler) – 0.0116 sec – 0.22%
Antispam Bee – 0.0098 sec – 0.19%
Ninja Popups – 0.0797 sec – 1.53%
BackWPup – 0.0914 sec – 1.76%
Contact Form 7 – 0.1213 sec – 2.33%
Duplicate Post – 0.0099 sec – 0.19%
Lollum Framework – 0.1957 sec – 3.76%
Oauth Twitter Feed For Developers – 0.0068 sec – 0.13%
Paypal Responder – 3.7374 sec – 71.83%
Redirection – 0.0299 sec – 0.57%
Revolution Slider – 0.1311 sec – 2.52%
TinyMCE Advanced – 0.0038 sec – 0.07%
WooCommerce Custom Product Tabs Lite – 0.0040 sec – 0.08%
WooCommerce – 0.4693 sec – 9.02%
Wordpress Seo – 0.2363 sec – 4.54%
Wp Smushit – 0.0415 sec – 0.80%
Wpgform – 0.0238 sec – 0.46%